Roronoa Zoro grew up in Shimotsuki Village, a village in the East Blue that is believed to have been founded by a descendant of the Shimotsuki family. Here, he learned swordplay from Koushiro before setting off on his own adventure.
Zoro manages to quickly make a name for himself as a bounty hunter but, due to his poor sense of direction, he fumbles about the East Blue before getting wrongfully imprisoned. After getting freed by series protagonist, Monkey D Luffy, the two go on to form the Straw Hat Pirates; a crew that will go down in history as the greatest to ever sail the seas.
10 BEARER OF KUINA'S WILL
Zoro learned swordsmanship from his master, Koushiro, in the Shimotsuki Village Dojo and, here, he found the first opponent that he could not beat, Kuina. Kuina is the daughter of Koushiro and she formed a strong bond with Zoro before tragically dying. Upon the death of his closest friend, Zoro requested that his master give the Wado Ichimonji to him so that he might wield it on Kuina's behalf.
After acquiring this sword, Zoro promised himself that he would become a swordsman man so strong that his name will one day reach the heavens for Kuina to hear.
9 THREE SWORD STYLE
Zoro is a master of the Three Sword Style and, for a long time, he was the only known user of this technique, until the students of the Isshin Dojo learn that the now infamous, Pirate Hunter Zoro, was a student of the Dojo.
This sword technique is unusual to say the least, but, through training, Zoro has made it his own and can use any of his blades to cut through the hardest of materials. Zoro is skilled enough to draw out the maximum potential of all his blades at once, meaning, each of his three slashes usually packs the same punch.
8 FORMER SWORDS
So far, Zoro has made use of quite the number of blades. Some as temporary placeholders, and others as a fundamental part of his sword set. The most famous blade that Zoro has previously wielded is Shusui, the famed blade of the legendary samurai, Ryuma the Dragon.
Zoro regarded this sword as a difficult one to tame at first but, eventually, he learned to wield it well before later returning it to Wano. Zoro has also wielded blades such as Uybashiri, which was a skillful grade sword he acquired in Loguetown from Ipponmatsu's sword shop.
7 CURRENT SWORDS
Zoro currently wields the blades Enma, Wado Ichimonji and Sandai Kitetsu. Each blade was skillfully crafted by a renounced Wano swordsmith, with Enma and Wado Ichimonji having been crafted by Shimotsuki Kozaburo and Sandai Kitetsu by Tenguyama Hitetsu, a descendent of the legendary swordsmith, Hitetsu.
Each of Zoro's blade has its own renowned background, with Enma being a blade strong enough to wound the unkillable, Kaido. Wado Ichimionji is famed for its beauty and is the heirloom of Zoro's childhood friend, Kuina. Sandai Kitetsu is a cursed blade that Zoro bet his arm on in Loguetown and, since then, it has not let him down, though it does tend to draw more blood than he wishes.
6 LOYALTY TO LUFFY
Zoro was the first person to join Luffy on his journey to become Pirate King, having been the initial members on the Straw Hat Pirates. The two share a very special bond and, though they don't usually verbalize this, it is evident in the way they act. The two are basically brothers and neither would hesitate to put either their dreams or lives at risk to save the other.
Originally, Zoro followed Luffy due to him saving his life but, eventually, he begins to trust and believe in Luffy. The loyalty he has for Luffy was highlighted when he was willing to give his life so that Bartholomew Kuma would spare Luffy, back in the Thriller Bark Arc.
5 THREAT LEVEL
Zoro currently has a bounty of over three hundred million berries and is a member of the Worst Generation. This marks him out as one of the most dangerous up and coming pirates, one whose power could shape the New Age of piracy. Zoro first rose to fame as a bounty hunter, one who would ruthlessly pursue his target until he was able to cut them down.
When the government learned that he had become a pirate, they quickly placed a bounty on his head but he's so far managed to evade capture. Zoro has been involved in critical fights that have shaped the destiny of the Straw Hat Pirates and his goal of being the Strongest Swordsman means, like Rayleigh before him, his threat level will only continue to rise.
4 SHIMOTSUKI HERITAGE
The Shimotsuki family was a powerful and renowned family in the Wano Country before it was invaded by Kaido. The family's last known leader was Shimotsuki Ushimaru, a man who bears a striking resemblance to Zoro. Another thing tying Zoro to this clan is Ryuma. Ryuma was often referred to as Shimotsuki Ryuma.
It is not yet known if it was merely his name or a title, but Ryuma is another person bearing the name of Shimotsuki that looks eerily similar to Zoro. This, combined with the character's sword skills, has led to many fans theorizing that Zoro is a descendant of this family.
3 WORK ETHIC
Zoro understands that his goal of defeating Dracule Mihawk is not something that he can achieve easily or with half-hearted effort. So, as often as possible, he will try and find time for training.
While other crewmates often engage in idle behavior in their free time, more times than not, Zoro can bee seen training throughout the night in order to sharpen his skills. This work ethic is why he's been able to grow as much as he has since entering the New World.
2 PATH OF ASURA
Zoro is on the Path of Asura. This path is one of hardship and pain, but one which ultimately leads to success. Due to the magnitude of Zoro's goal, it was never going to be easy for him to achieve his dreams, and this is the reason he decided to walk the path of Asura.
Though it is fundamentally a path of pain, the Path of Asura guarantees success as long as the individual walking the path has enough strength to endure all the pain involved. Zoro has shown time and time that he has what it takes to walk on this path and it will one day turn him into a legend.
1 POST TIMESKIP
After joining up with the crew, the most striking change in Zoro's appearance is the mysterious scar he received over his left eye. Much has yet to be revealed about that eye, but many fan theories have been made.
Zoro trained under the tutelage of Dracule Mihawk on Kuraigana Island, which greatly aided his development. This training would often involve Zoro training with Humandrills on the island. Mihawk taught Zoro how to imbue his blades with Armament Haki and, by the look of it, Zoro also picked up some knowledge about Observation Haki during this training period.