A Black hole is a super condensed object.
Many are formed by the collapse of a star. Some are discovered because they are part of a binary system. At the centre of each Galaxy, there is a super massive Black Hole
When looking at the creation of the universe, there does not seem to be any reason for material to form into a pattern of Galaxies. But most material known is in one.
A Galaxy is held together by gravity. The centre of a Galaxy is that force. This is not a collapsed star. It is a collection of material, probably super condensed, creating places that can orbit the centre of the Galaxy