Yamcha was born in 733 - the same year
as Bulma and Tien. He started off a bad guy - he tried to rob Goku
and Bulma in Dragonball. He kept a companion named Puar, an adorable
blue shape-shifting cat. Yamcha was scared of girls so Bulma was
able to keep in him straight at times. Ultimately Bulma and Yamcha
came together as a couple after he reformed his bad boy ways and went on
the side of good.
In the beginning of Dragonball Z we see him a
lot - he is a brave warrior. He is a bit of a cad and it is mentioned that
he cheated on Bulma - but they make their way back to each other again...
and again... and again. Vegeta ends up killing him (via
Saibamen) and Yamcha trains on King Kais planet. Bulma was sad about
his death - they had been together on and off for a long time - over a
decade at that point. Yamcha comes back to Earth and seems to go
downhill. He gets weaker by the episode... I dont just mean his
strength, I mean his bravery too. He does some battles and puts up
his best effort but his heart isn't in it. He is very jealous of how
Bulma acts around Vegeta. Eventually Yamcha and Bulma split for good
as she is now with the Saiyan Prince. By the end of the series he
doesn't fight anymore, he has completely wimped out. A tragedy in my
opinion because Yamcha had potential to be quite a stud; instead he
becomes a loser.
There is tons more info on Yamcha but my site
is for the Saiyans, not for the "weakling" that Vegeta detests.