There are four types of baptism, and "pouring baptism" is one of them. It is known as affusion, which comes from the Latin word for "pouring".
The other forms of baptism are:
- Full Submersion
- Partial Immersion
- Sprinkling
Pouring generally means holy water is poured on the head of the person being baptized. More often, this is practiced with denominations where child baptism is common practice.
The reason being that submerging an infant under water can be difficult, dangerous, and cruel.
Most people feel pouring water on the head to be sufficient.