They are in the middle of wilderness and thousands of people have followed them hoping for a miraculous healing. They have been journeying all day so the food the people brought with them is pretty much run out and Jesus wants to feed them. All they can find is 2 fish and 5 loaves of bread. After giving thanks Jesus hands it out with more than enough to feed everyone. This shows us that no matter how little we are able to give to God, He can multiply it to be more than enough. We just have to be willing to give it.
This miracle was enough for the 5000 people to believe that Jesus was the Messiah and they wanted to make him king. Jesus had to escape to stop this from happening, 5000 people is a lot and have the power to make it happen. The Jews believed the Messiah would come, save them from their oppressors (in this case the Romans) and set up his kingdom on earth. Jesus did come to set up his kingdom but now in the way that they were expecting.