A tree is one of the widespread data structures in computer science and a natural way to model certain subject areas. Everyone will encounter trees as a data structure in one form or another, even if they're not into computers or programming in general. The most obvious example is a family tree, and if we're looking for something more up our street, a file tree.
HTML, JSON, XML, and many others have a tree-like structure. Comments and product catalogs on websites can also be tree-like. Any hierarchy is a tree by its definition.
