A file system is the way an operating system organizes and stores data on a device. Files are individual units of data (documents, photos, programs), and folders (directories) group files hierarchically. Understanding paths — the address of a file within the folder tree — allows you to find, move, copy, and delete files reliably. Good file organization prevents lost work and makes backups and sharing much easier.
Practice by creating a personal folder structure for a project: make subfolders, move files between them, and rename them consistently. Then use the OS search tool to find a file you misplaced.
Think of your computer's storage like a large building with rooms inside rooms. The entire building is your hard drive or storage device. Inside are rooms (folders), and inside those rooms are smaller rooms (subfolders) and items (files). A file is a single unit of stored data — a document, a photo, a spreadsheet, a program. Folders exist only to group files in a meaningful way for you. This nested structure is called a hierarchy, and it is how every modern operating system (Windows, macOS, Linux) organizes storage.
Every file has an address within this hierarchy called a path. On Windows it might look like `C:\Users\Alex\Documents\Work\report.docx`; on Mac or Linux it looks like `/Users/alex/Documents/work/report.pdf`. Reading a path left to right, you are walking down from the top of the building (the drive) through each room (folder) until you reach the file. Understanding paths matters because when programs ask "where do you want to save this?" or "where is the file you want to open?", they are asking for the path.
One important thing to know about file extensions — the letters after the dot at the end of a filename (like `.docx`, `.jpg`, `.pdf`) — is that they tell the operating system what kind of file it is and which program should open it. A `.jpg` file is an image, a `.pdf` is a portable document, and so on. Operating systems sometimes hide extensions by default, which can be confusing. If you rename a file and accidentally change or remove the extension, the file may become unreadable.
A common mistake is treating the Desktop as permanent storage. The Desktop is actually just a special folder, and on many systems it is not included in automatic backups. Similarly, the Downloads folder tends to accumulate files that are never organized. Building a simple, consistent folder structure — for example, separate folders for work, personal, and school projects — makes files much easier to find and back up reliably.
Finally, remember that "deleting" a file usually just moves it to the Recycle Bin or Trash. The file is still taking up space and can be restored until you empty the bin. This is a safety net worth using — before you permanently delete something, ask whether you might want it back within the next week or month.
This is a foundational topic with no prerequisites.
No prerequisites — this is a starting point.