A godparent is a person who sponsors a child at baptism/christening and takes on a commitment to support the child's spiritual development. In the Church of England, a child can have up to 3 godparents.
At the christening, godparents make declarations on behalf of the infant, affirming Christian faith. They commit to helping the child grow in the Christian faith.
In practice, godparents are expected to maintain a relationship with the godchild — sending cards and gifts on birthdays and Christmas, being interested in their life, and being a trusted adult presence as they grow. The extent of involvement varies enormously.
Choose people who will genuinely remain present in your child's life. The formal religious commitment matters to some families more than others, but the relationship is what endures. It is an honour — but also a responsibility. Ask early and be clear about your expectations.