Git very much has directories, it calls them "tree": a commit links to a tree, which links to a number of trees or blobs associating each with a name: https://git-scm.com/book/gr/v2/Git-Internals-Git-Objects

A blob is a file (ish, it can also be use for some other things since it's not intrinsically named), a tree is a directory.

However Git doesn't treat filesystem directories themselves as first-class e.g. you can't version an empty directory. A tree only exists in order to contain sub-items (ultimately blobs).