mutual aid is solidarity, and should challenge the systems that create hierarchies

charity is hierarchical, and takes for granted (ie, works within) those systems that create hierarchies.

I think also though when someone refers to "charity" they are usually referring to big nonprofits or wealthy people philanthropy. Idk the exact definition of charity or charitable, but I suppose you could make the case that mutual aid is "charitable," or that "charity" does not necessarily need to be this hierarchical, systems-enforcing act. And I suppose mutual aid does often include some aspect of "charity."

But in our current vernacular, charity usually refers to hierarchical giving which seeks to enforce those systems that make charity necessary. It's a temporary reallocation of resources. whereas mutual aid seeks to challenge those same systems which charity upholds. mutual aid builds up sustainable communities, not communities which remain dependent. The difference is where the saying "solidarity not charity" comes from.