file extensions connect files to the right programs by telling the computer which program to use to open your files!

When you hear things in trainings like ‘.swf’ or ‘.jpg,’ those are file extensions. Some have even become part of our regular vocabulary without many even knowing that they’re talking about a file extension! An .mp3, for example, is a type of file, even though now the word is becoming synonymous with ’song.’
What is it, and what does it do?  This is important.  A file extension tells your computer what file type it’s dealing with so it knows what program it should use to open a file.  For example, can you imagine opening an .mp3 in Microsoft Word?  It just wouldn’t work.
If you open a file in microsoft word, you’re opening a .doc file. It gets confusing when a program opens and uses a bunch of different file extensions.
For example, why do we need .mov, .avi, .flv, etc… they’re all video types, right?  Why do we need .wav and .mp3?  They’re all audio, right?  Yes, but the difference is size in those examples.  A song in .wav is a different than the same song saved as a .mp3.  Imagine a piece of data is the size of a marble.  A file is made up of a bunch of data.  If you filled an entire classroom full of marbles and called it a song file, that would be size of a song as a .wav.  If you put a few marbles in a mason jar, you’d have the size of the song as an .mp3.  Now you’re seeing the advantage of using different file types, right?  File extensions indicate the file type -that’s important.
How many file types are there?  Hundreds, so don’t bother trying to learn them all.  The good news is that there are way fewer that you’ll actually have to worry about, and most, you’ll find, you already know!  In the comments below, I’m going to start a list of common file types. I’m hoping folks will help out by listing file types they run into in virtual education with ’the skinny’ on each file type.  If we get a big enough list, I’ll compile it to a table and share it!