This problem shows another basic idea which occurs regulary during endgame ko fights. It is an easy problem, too, but don't worry - there will be more difficult ones soon!
AW[ba][da][bb][cb][cc][cd][be][ce][de][ee][cf][dg]AB[ea][db][eb][dc][dd][ed][fd][fe][df][ef][gf][fg]C[No komi, no prisoners - black to play and win!]
;B[ca]TR[cg][eg]CR[ca]C[Thanks to the exchange of the marked stones there is no white ko threat left, so black can connect the ko and wins by 1 point. RIGHT])
;W[da]CR[da]C[If black takes the ko at once there remains a white ko threat at the bottom, white can recapture the ko and a jigo results.])
;B[ff]CR[ff]C[Ignoring the white ko threat gives black not more than a jigo.])))