C:\Users\wgt04\AppData\Local\Arduino15 is the "data folder" of the Arduino IDE. It is used for several things.Your Arduino IDE preferences are stored in C:\Users\wgt04\AppData\Local\Arduino15\preferences.txt.The Boards Manager and Library Manager index JSON files are downloaded to C:\Users\wgt04\AppData\Local\Arduino15 and cached in C:\Users\wgt04\AppData\Local\Arduino15\cache. Their activity is logged to C:\Users\wgt04\AppData\Local\Arduino15\logs.Hardware packages installed via Boards Manager are installed to C:\Users\wgt04\AppData\Local\Arduino15\packages.Hardware packages and libraries are downloaded to C:\Users\wgt04\AppData\Local\Arduino15\staging before being installed. The staged files are left under that folder to make re-installation faster should these files be needed again. Over time the toolchain archives in that folder can add up to gigabytes, so you might look there if you ever need to free up some disk space.C:\Users\wgt04\AppData\Local\Arduino15 is created automatically. C:\Users\wgt04\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.8.2 was only created when you chose to update Arduino AVR Boards to 1.8.2 via Boards Manager.
You might want to look in to the "portable" feature of the ide. That'll let you keep all the arduino stuff in one place