Baptism is a physical act. You physically enter into the water. Your body goes under the water and is lifted up out of the water again. This physical action represents a great spiritual truth. Romans 6:1-14 describes this beautifully, telling us how our salvation is a spiritual baptism that identifies us with Jesus who died, was buried, and rose again. Our physical baptism publicly identifies us as Christians and pictures this truth for all to see.
No. Baptism pictures our salvation but does not save us. We are saved by God's grace, not anything we do to earn it – including baptism. (John 3:16, Ephesians 2:8-9)
Baptism is an ordinance. That means God ordered it to be done. He gave this ordinance to the church: to baptize those who become Christians. It is as if you are preaching your first message to others through this symbolic demonstration. If you need to obey God by getting baptized, make sure you invite your family and friends to be witnesses of your testimony.
If you are a Christian (you have been born again by putting your faith in Jesus to save you), you can and should be baptized. (Acts 8:36-38)