How browser cache web site pages

i am looking for very basic question.

i am not sure that always browser cache pages we visited. so my question is when browser cache web site pages? whatever site we visit by browser then browser cache each pages ?

if yes then how long or many days browser cache each pages ?

how browser know it has to load pages from cache instead of loading from remote web server?

How browser compared the remote web site pages changed and need to load from there instead from cache version?

please help me with knowledge. thanks