If you take all parts and put them together, you have all things. The entire collection. It is whole.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
to look at everything
to do everything
to eat all of it
I'm going to buy all the apples.
I got good test scores in all subjects.
Who the hell ate all my bacon cookies?!