Answer:
Acquiring a company typically includes acquiring all of it's assets and liabilities, which would usually include it's name, business assets, plants and locations, employee relationships, and brands.
Acquiring a brand, though, can also be a matter of outright sale from one company or holder to another. If a company that produces a popular widget goes out of business or changes focus to another product line or type, the right to produce that widget, under the same well-known name, can be sold to another company that might wish to enter that market or enhance it's market share.