Please excuse my military ignorance

I am researching a man who died on 18th September 1918 and is buried in the Suez War Memorial Cemetery in Egypt. He was enlisted into the Royal Warwickshire Regiment and I have seen online that during the First World War it raised 30 battalions. My man was in the 1st Garrison Battalion which was formed at Weymouth in August 1915 and moved to Egypt.
I have two questions which I hope some kind person could help with:
1) What is the distinction of a 'Garrison' Battalion as opposed to an 'ordinary' one?
2) Would there be any way of finding what the battalion was doing there at that time, other than going to Kew as I will not be able to get there for a couple of months?
Needless to say his service records have not survived, but his medal card shows that he recived the British War Medal and the
Victoria Victory Medal.
All help appreciated!
John