[Q] I have some simple questions about the storage/emulated folder that need answers topic

The longer I have my Shield Tablet, the internal storage space seems to slowly vanish more and more. I have been constantly clearing cache, as well as uninstalling more and more apps. The entire internal storage folder (labeled storage/sdcard0), takes up a total of only 3.77 GB according to ES File Explorer, yet I have less than 2 GB free. I have noticed there is a folder labeled: storage/emulated. Within this folder are "0" and "legacy"... Both of these folders appear to be complete clones of the sdcard0 folder (each are exactly 3.77 GB as well). All three of these folders add up to equal the total storage used on the internal storage. So can I really only use a third of the internal storage since everything is duplicated 3 times? Is it safe to delete the contents of either of the 2 folders within storage/emulated? What is the purpose of these folders?