Every time you log in to the site, you have the option of checking a box next “Remember Me” under your credentials. The key to this function is that it extends your session on the site from 2 days to 14 days, as long as you do not log off. So basically, if you finish your current browsing session and close the webpage or browser without logging off, then you still will be logged into the site when you return if it is within 14 days (2 weeks). Normally, you would be able to return within 2 days and still be logged in. The key to this, though, is that any time you log off, you immediately stop your session. So ticking the “Remember Me” box will have zero functionality.
Just to add, there is obviously a security component to this topic. It is always safer to log out in terms of security and I suggest you do so if you are using any type of public computer. If you are at home and there is no security risk present, then it is up to you whether you want to stay logged in using the “Remember Me” functionality. If you want to stay logged in, then just don’t click “Log out” at the end of your browsing session.