You have some pretty cool answers to your question here as I read them, its really simple though, baptizeing is being fully emersed under the water and the other is just sprinkles of water dribbled over your head, our religion believes in going to the river and baptizeing...just like Jesus was.
Baptism is being immersed under water, a result of making a profession of faith in Jesus. It is an act of obedience to Christ, but does not save in itself. Christening is a sprinkling of a young child or infant and some denominations consider this an act to salvation. But it does NOT save. A young child or baby can NOT make the decision to choose Jesus or not. So it basically is just a ritual or tradition. A person needs to be old enough to be able to decide whether or not to follow Christ.
Per the thief on the cross....there are times when you can apparently enter Heaven under special circumstances. For instance, if you were perhaps living in a third world or remote country and/or had never been exposed to Jesus whatsoever...you would not be held accountable for not receiving sacraments, living a Christian life, etc. I don't remember if we do know the thief's background, but this could be one of those circumstances...where he really had no knowledge of Christ and was forgiven of his sins directly by Christ. If you have been sufficiently exposed to Jesus and have had the reasonable chance to be baptized, and lead a good life, however, the Catholic belief is that you would be held accountable for not doing so.
Actually, there is a lot of confusion here. Baptism is the act of using water as a sign of salvation for ANY person (infant, child, or adult). The amount of water is completely irrelevant; baptism can be done by pouring, sprinkling, or immersion. All three forms are valid baptisms, and all three are called BAPTISM regardless of the age of the one being baptized.
CHRISTENING, on the other hand, is a totally separate issue. It is the short naming ceremony that follows infant baptism in the Roman Catholic Church. Most Protestant churches do not christen; either they baptize infants or they have infant dedication ceremonies (which are NOT christenings). It is always safest to use the term "baptism" in sacramental churches or "infant dedication" in non-sacramental ones. In general, stay away from the term "christening".
Well, there is a big difference. In Scripture, How was Jesus Baptized? How was the Eunuch baptized? How did John the Baptist baptize? They were all immersed. If you look to scripture to find your answers, you will not go wrong. No where in scripture do you find the use of Christening. What Baptism does show is that someone has made a profession of Faith in Jesus Christ and it represents us dying like Jesus did and being raised like Jesus was to a new life in Christ. I know the great reference is found in Matthew 28:16-20, the great commission.
