deleting apps from itunes library

my phone is sooooo full of apps ( and pics) that its going to crash.. i cant do updates or take 1 picture.

so, I am on computer on itunes. i have my apps up on the screen. There are ones i want to delete... forever,

and there are ones i want to delete ... temporarily so i can use them again.

i have deleted ones off of my phone that i dont want anymore. I think i need to still delete these in itunes though ( for space).

so, it gives me 2 confusing options.

it says "do one of the following"

"remove item from itunes library; click keep file"

or

"Delete the item from your computer. click move to recycle bin. The item is removed the next time you empty the recycle bin".

so what do i choose 1. to delete forever and 2. to delete temporarily 9 like put in a folder to use later ??? TY