Specifically, which churches practice child-baptism but not confirmation?
A Brazilian friend recently shocked me by saying that her church does not practice confirmations. The wiki page for Baptism has an extensive comparison of baptism rites, however it does not go into detail about confirmation.
As I understand it the following is standard in the major denominations. Perhaps it would be useful to explain the differences relative to this.
Baptism is an induction into the Christian faith which necessarily involves a public declaration of faith and wetting/immersion/submersion with water. If the baptism is performed before the person has 'come of age' (usually coincides with puberty and reaching the age of 13 years), then the parents and godparents make the declaration on behalf of the child.
Once a baptised child has 'come of age' (as described earlier) they may choose to undergo confirmation, which is a public declaration of faith and does not necessarily involve water.
A person can only take part in communion if they have undergone an adult baptism or confirmation.