A picture is worth a thousand words, right?
There are a number of different styles for each of these headdresses (i.e. midnight blue, navy blue, khaki, faun, some without checquered pattern, different coloured checquered pattern ... it‘s complicated).
However, the forage cap is the "peaked cap" similar to the one worn by police officers when they‘re wearing a shirt and tie.
The wedge cap favoured by the Air Force is somewhat similar in design to something once called an "overseas" hat (often seen tucked under the epaulette in WWII movies), and the glengarry is marginally similar except that the glen has tails that hang down in back.
The balmoral and tam‘o‘shanter (TOS) are roughly the same thing (to outsiders), and there‘s also the Kilmarnock bonnet - a confusing mixture of tails and no tail, checquers and not!
So, with no further ado, here are a few pix:
First, a balmoral (okay - it‘s a little crooked, but heck ... the model is just so darned cute).
Then, one version of the glengarry.
I don‘t have a forage cap, therefore no pix!