Aloe vera:
much bigger plant that clumps more slowly and most often has bright yellow flowers tightly packed on the raceme.
Aloe officinalis - the one that is often sold as Aloe Vera in grocery and big box stores:
much smaller plant often spotted that clumps really fast - probably explaining its much wider availability - with salmon-orange flowers that are more sparsely distributed on an often much taller raceme.
I cannot advocate which plant to use over the other, or for what, since I do not have any experience with their use beyond using Aloe vera for sun burns a long time ago. There is a lot of information out there that might help, though it is not always clear where fact ends and fiction starts.
