There are two ways to answer this question. One is to look at the actual definition of “maroons” while the other is to look at what the existence of maroons meant for African American history.
Maroons were slaves who escaped from their owners and formed independent communities with other escaped slaves and, sometimes, with indigenous peoples. The term does not apply to slaves who, for example, escaped to the North in the United States. It only applies to those who formed their own communities. There were larger communities of maroons in the Caribbean and South America than in the United States, but there were some maroon communities in what is now the Southeastern US.
Figuratively, what maroons represent is the spirit of African Americans. Maroons represent the idea that African Americans were not defeated by slavery. It was once common to say that African Americans were relatively docile as slaves and did not resist slavery to any great degree. The presence of maroons is a symbol of the falseness of that idea. Maroons represent the fact that African Americans were always trying to find ways to resist slavery and would escape and form communities of their own when possible.