When Jesus was physically on earth, He regularly gave the invitation for people to follow Him.
The invitation had both spiritual & practical implications & it still does for us today. Historically, people who followed Jesus' teachings & put their trust in Him for an eternal hope - Heaven - have been called 'Christians'.
We often use the term 'Jesus follower'. Trusting Jesus means we no longer rely on our own merit or standards to be considered 'good with God'. It means to trust that Jesus' death on the cross fulfilled all that was required for the forgiveness of your sins ('sin' means 'missing God's mark').
The promise resulting from that is an eternity with our Heavenly Father (in Heaven), and the experience of a new kind of life here & now.