Entry and Reentry on a tourist visa

I know you can stay on a tourist visa for 3 months.  Can you leave the Schengen Zone and then reenter?  How long would you have to leave in order to reenter for another 3 months?  Is that possible?

I know that for some countries there is a system 90-90-180 or 90-90-360. It means if your visa is open for 6 months (which is 180 days) you can enter only for 90 days during this period. If it is open for one year(360) you can enter twice for 90 days with a breake for 90 days. So if u stay for 3 month once next time u can come will be in 90 days. I hope it s more or less clear. But if u have visa which is open just for 3 months u can apply for the other one after first expires.