Forage Cap, Issued in the good old days. Still issued. Made you look like someone from Thunderbirds or a popcorn seller in the movies. Replaced by the Beret.
Nicknamed 'Side Cap' since they were somtimes [sic] wore one one side. __________________________________________________________________________________________ Yet again, inaccurate posting. The beret did not replace the Cap - Service Dress. The Cap - Field Service did. This in turn was replaced by the Cap - General Service, or 'Cap Ridiculous'. This is what the beret replaced.
As for the side cap, this had its origins in the Victorian army for undress wear. A later variation of this was the (already mentioned) Cap - FS, which came in a variety of regimental patterns as well as the more often encountered khaki that became general issue around 1937. The side cap and forage cap are two entirely different items of head wear.
By the way this is a full stop:. This is a comma:, Two entirely different uses. Get a fcuking grip!