Mac storage basics · Finder tools for finding space
What can Finder's Get Info window tell me about a file's size and location?
Short answer: Press Command-I on any item. Get Info shows its size, where it's stored, its kind and its created and modified dates; for a disk it shows format, capacity and free space.
Select a file or folder and press Command-I (or File → Get Info). The General section shows its kind, its size, where it lives (the Where line), and when it was created and last modified.
For a disk, Get Info also shows its format, capacity and available space. You can open several Get Info windows at once to compare items.
If a size looks odd, see why Get Info shows two sizes.