Why is my memory so full?

thats not memory (RAM) , but SSD or hard disk storage.

See here for answer about the OTHER which is taking up space:

http://pondini.org/TM/30.html

and here:

http://pondini.org/OSX/DiskSpace.html

See Kappys excellent note on the rest of “other” files taking up your space:

What is "Other" and What Can I Do About It?

Its not applications, its being reported incorrectly.

You need to reindex your system.

http://support.apple.com/kb/ht2409

also SMC reset your system.

SMC reset

1. Shut down the computer.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
   Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.

It doesnt matter what that graph says, its inaccurate. Everyone has "other" taking up space, most very little.

Obviously you dont have 370gig of APPS, nor do you have 0 taken up as OTHER.

otherwise its local snapshots....read about same here::

http://pondini.org/TM/30.html

Open your terminal application and enter the following bolded command. Copy it exactly as it is and paste it into your prompt. It may take a minute or two to run. Let it. Post the output in your reply.

du -sh /Applications;echo;du -sh /Applications/* | sort -nr

(if anyone has a tip on how to make this command sort properly (not just strictly numerically) it would be appreciated! cough cough Linc Davis cough cough)

Rebuild the Spotlight index. If you try to search now from the magnifying-glass icon in the top right corner of the display, there will be an indication that indexing is in progress.