What is an analogy between file and folders?

A good analogy maybe a cupboard and the contents of the cupboard.

In your kitchen, for example, a food cupboard has many individual items of food in the cupboard. In the pot cupboard are individual pots and pans.

A folder is like a cupboard, inside the folder is individual files. Like cupboards, folders can be used to hold different kinds of files. For example a folder called 'music' can hold files that are different music files/recordings.