Gohan is the eldest son of Goku and Chi-Chi and was named after Goku's adopted grandpa. He is also the very first half-blooded Saiyan and during several moments in the series was the most powerful fighter on Earth and in the Universe.
Gohan is a kind person and being pure of heart can ride the Flying Nimbus. He is also a very smart person due to extensive studying under Chi-Chi's supervision
In the English dub of the Dragon Ball Z anime Gohan was originally voiced by Ocean Group voice actor Saffron Henderson for the Saban and Funimation version of the series. Henderson also voiced Gohan for the original English dub versions of the first 3 DBZ films.
When Saban left Funimation they recast the role and Gohan was then voiced by Stephanie Nadolny for the Funimation version of Dragon Ball Z from the Ginyu saga onwards. Nadolny also voiced Gohan for the re-dubbed episodes originally voiced by Saffron Henderson, the Dragon Ball Z films, plus the re-dubbed films originally voiced by Saffron Henderson.
However Saffron Henderson continued to voice Gohan in an alternate dub for Europe and Canada up until the Cell Games saga. She left the series during that time because it conflicted with her planned wedding.
So for the Cell Games saga in the Ocean Group dub Gohan was voiced by Jillian Michaels.
For Dragon Ball Z Kai Gohan is voiced by Colleen Clinkenbeard.