The people have been with Jesus all day; they are hungry and without food. Jesus asks how much food is available; the report is merely five loaves of bread and two fishes from a boy. [John 6:9]
Surely out of more then 5,000 people, other people there also have some food, but they are keeping it to themselves (which seems wise and prudent). However, one boy is willing to share what he has. Because of that, his small gift is used to feed all those people.
We don’t have to give Jesus something huge or beyond our means, but we do need to give him what we have. When we do, Jesus can do great things with it.