Discipleship is a central theme in the gospels. It is an ancient idea that is not well understood these days.
We naturally (though not necessarily consciously) look to others as our models for the way to do life. Discipleship is the process whereby we do this in a deliberate and focused manner.
Jesus calls us to follow him. Not as an casual observer who shows passing interest like on twitter. But as those who focus on him and his ways so as to internalise Jesus’ values and learn his ways of relating to others.