enlarge means make something larger enough for you to see. ex: He enlarged the image on your phone (like zooming) expand means adding something more and more to the group and thereby make it bigger ex: The football stadium has expanded to seat more number of spectators.

It’s not so easy to explain the difference. They can both be used with the meaning “to become or make bigger”. Sometimes they are interchangeable: "Expand/enlarge one’s vocabulary." It seems that the difference is mostly about collocations (the fact that certain words are often used together). For instance you say “Metal expands when heated.”, but you say “He has an enlarged spleen”. Why not an “expanded spleen”? I don’t know. It would be common to say “They've enlarged the kitchen by building over part of the garden.” When talking about a business or a company or the economy it’s common to use “expand”: “I don't think we should expand our business in the current economic climate.”

As verbs the difference between enlarge and expand is that enlarge is to make larger while expand is to change (something) from a smaller form and/or size to a larger one