Session - when they expirate ?

Hi, I was looking all over the internet and I don't understand when and how does the PHP session expirate. I suppose that it happens when the user is inactive. On my website I don't use cookies for session and it has standard php.ini configuration: session.gc_maxlifetime = 1440 session.gc_divisor = 100 session.gc_probability = 1 session.cache_expire = 180 So, does this mean, that if the visitor is 180 minutes inactive it automatically deletes the session ?? Thanks, Martin