Quote from Fail_Field
Factory reset wipes all data from the device that was created by the user. The only things it won't wipe are the things that were installed by the manufacturer.
false. factory reset does not touch certain files. like camera pictures folder. and even some data in the root directories. this could include certain minecraft files ( i don't know i never touched or needed to touch my minecraft pe files) i did many factory resets and my pictures and videos and downloads are all safe. always. (therefore when i install a new ROM i use megawipe to delete everything and start anew).