Subfolder location - subfolders branch off of a folder, therefore, they exist at least one step down from a main folder. Subfolders can have subfolders. File definition - file is the smallest chunk of user information which can be manipulated in a computer. You create a file using software on your computer. File location - files exist within drives, folders, and subfolders.
File extensions define the file type for the computer.
For instance, a document created using MS Word will have the file extension .doc. This tells the computer that the file you are accessing is a Word document. There are many file extensions for computers, usually your computer will apply the correct extension to a file as you save said file. Using lower case for file and folder names reduces the variable set. The web is case sensitive.