How do large businesses impact small businesses?

Larger business earn more profit than smaller businesses allowing for them to build more and own more stores. Thus pushing customers away from smaller more localized businesses.

For example take Wal-Mart, a large business, they are a clothing store, house item, pet store, and pretty much everything else. Why would someone visit 6 little stores that sell different items when they can go to Walmart and get all their items in one store.