Through baptism, Christians are grafted into God' family tree; you are claimed by God (Isaiah 43:1)! Together, the universal Church is the Body of Christ on earth, as Paul says in his first letter to the Corinthians (12:12-13):
For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ. For in the one Spirit we were all baptized into one body—Jews or Greeks, slaves or free—and we were all made to drink of one Spirit.
The Christians' life is centered around baptism, where daily we die to sin and rise to new life in Christ. Our old selves (our Adam/Eve) are washed away, and we no longer live unto ourselves but as a member of the Body of Christ. In baptism, the one being baptized makes these promises (for infants, the sponsors speak on behalf of the baptized--in confirmation they are able to speak for themselves):