Hi folks

Heres hoping one of you gurus can shed some light on this dark art

Im using version 4.9.2 and trying to get my head round the standard caching options available and what they actually do  -  I can see only  two areas that relate to cache

1) Host Settings / Performance
( I have set Module Caching Method to Memory, Performance Heavy Caching  - as running on own server so should have memory available for cache )

2) HTML Module settings - Cache Time (default 1200)

Does this mean only modules which have a cache option set to >  0  (ie the HTML module) are  being cached  ? 
There is no caching at page / tab level  going on or for that matter any other caching ?

i have tried changing settings for HTML module Cache Times from 0 to 1200 but havent noticed any difference - also if i update an  HTML module it makes the changes available immediately which suggests either its not in cache or the cache is being cleared?

Is there anyway of telling what if anything is being cached

thanks

J