Goku is a powerful Saiyan from Planet Vegeta. Known to his fellow Saiyans as Kakarot, he was known as Son Goku when he was raised on Earth. Son Goku was considered a fitting name for the boy because of his strange monkey tail. His name originated from the mythological Chinese Monkey King:Sun Wu Kong.
The Dragon Ball series follow his growth as a character and his adventures of protecting the Earth from evil forces. Goku's above average strength and speed combined with his youthful attitude gives him the ability to tackle all odds and any challenges ahead of him. He strives to be more powerful by training with people he thinks are stronger than him.
The adventures of Goku begin when he encounters a young girl by the name of Bulma, who is looking for the legendary dragon balls. When all seven dragon balls are found,the magical dragon Shenron appears and grants a wish. Goku dutifully follows Bulma, as he was encouraged to search for the dragon balls by his earthly caretaker, Son Gohan. Unbeknownst to him, the heirloom left by Son Gohan was a dragon ball all along.
Seeking to strengthen himself, Goku sets off in a path to fight the world's fiercest warriors in the famous World Martial Arts Tournament. Despite his intense training and impressive strength, Goku has found himself in the hands of defeat but faces it with a smile. He knows that this is even more of a reason to get back up on his feet and keep training. The results of his intense training has given him the strength to overcome an entire evil army armed to the teeth with heavy weapons and machinery as well as a demon and its entire army.
Goku, under solitary training, has found a giant tower that is said to reach the sky and was rumored to hold blessed water that will amplify one's strength to new heights. He found out that when going to the top of the tower was treacherous, he endured the many lightning bolts and exhausting climb. This endeavor took him the omnipotent creator of the dragon balls himself, Kami-sama. As far the the dragon ball saga goes, this is as intense as Goku’s training gets. With this training against earth’s god, Goku finally earns himself a victory in the final World Martial Arts Tournament.
This time around, Goku has grown into a full adult and is married with two children: Gohan, named in honor of his caretaker, and Goten, the much younger of the two. Just like before, Goku is always putting himself through intense training. With foes from the previous saga now turned to allies, Goku has found himself in a group of formidable training partners and heroes known as the Z fighters.
A lot about Goku’s mysterious origin is explained. We find out that Goku’s original name is Kakarot and that he was born on Planet Vegeta, home to the Saiyan warrior race, few which remain alive. The survivors were enslaved by the powerful evil overlord Frieza. Out of this invasion also came a rival (but soon-to-be ally) who was once the prince of Goku’s home planet. That rival’s name is Prince Vegeta.
This is where we get to see the true untapped potential of Goku’s power and his compassion for people. Legend says that on planet Vegeta, Saiyans were able to unlock immense power by undergoing intense emotional trauma during battle or training. At this point of time, Goku has experienced the loss of his closest ally, Krillin, at the hands of Frieza. The overbearing guilt, sorrow, anger and dedication to protect planet earth allowed Goku to transform into a super saiyan. This transformation physically changes Goku’s appearance as his hair now defies gravity and turns blonde, his eyes become green, and a golden aura surrounds him. He has tapped into even more greater strength than before to fight and protect planet earth from Frieza’s plan of terror.
We start to see a shift in Goku’s personality as we progress in this saga. He's not the only one that undergoes intense training anymore. Goku now puts his son Gohan, through training that is just as intense . Although he means well for his son, he is not attentive to his needs at times and even occasionally puts his son in danger. This can be attributed to the fact that he did not grow up with parents and has only known the guidance of his caretaker, his son's namesake.
By now, Goku is considered Earth’s Mightiest hero by most. His victory over some of the most villainous lifeforms have shaped Goku into a being who has fully tapped into his potential. Or so he thought, that is, until he met the god of the destruction in the universe, Beerus the destroyer. When both encounter one another, a small feud breaks out into a global scale that ultimately leads to Goku protecting earth from destruction yet again. This battle showed yet another transformation of Goku. This physical appearance changes his blonde hair and green eyes to red hair and red eyes. In this form, Goku is known as a super saiyan god. As we have seen so far, there is a pattern occurring. Goku’s quick adaptability and willingness to protect the people of the earth can be seen as his own form of training. His ultimate goal is to be the strongest and in his journey, he has met with constant powerful threats that he treats as valuable experience. In each battle, he is met with circumstances that incentivize him to reach even greater heights within the heat of battle.