A food CHAIN only FOLLOWS just one path as ANIMALS find food whereas a food web shows the many different paths plants and animals are connected.
Food chains SHOW a single path of energy flow through and ecosystem. It shows a single ITEM that an organism eats, but a food web shows all the different paths of energy flow and multiple items organisms eat.
A hawk eats a snake, which has eaten a frog, which has eaten a grasshopper, which has eaten grass. is a food chain whereas A hawk might also eat a mouse, a squirrel, a frog or some other animal.