Stop Vs Affricative Sound

A stop sound is pronounced with a sudden release of breath. In other words, it is produced by stopping air at some point and suddenly releasing it

Affricative sound is a composite speech sound consisting of a stop and a fricative articulated at the same point (as `ch' in `chair' and `j' in `joy').

The following are the explanations from Answers.com

plosive
(plō′siv)
n

Any speech sound made by impounding the airstream for a moment until considerable pressure has been developed and then suddenly releasing it (e.g., b, d, and g). One of two types of stop consonants, the other being affricative (e.g., ch).


affricative

(əfrik′ətiv)
n

A fricative speech sound initiated by a plosive.