John 15 is a part of the Bible that talks about how Jesus is like a vine (like the plants that grow grapes), and we are like the branches that grow off of it.
Jesus is saying that if we want to be close to him and do what he wants us to do, we have to stay connected to him like a branch stays connected to the vine. Just like how a branch can't grow or produce any fruit without being connected to the vine, we can't be good and do good things without being connected to Jesus.
Jesus also talks about how God is like a gardener who takes care of the vine and cuts off any branches that don't bear fruit (meaning they aren't doing good things or being kind to others). But he also takes care of the good branches, pruning them (like cutting off dead leaves or branches) so they can grow even more and produce more fruit (meaning they can do even more good things and be even kinder to others).
So basically, John 15 is talking about how important it is to stay close to Jesus and do good things, so we can grow and be even better people.