Models have the option to enable the recording of their public shows, so if you go to a model’s room and see a “START REC” button at the top, it’s your lucky day.
You can record the public show paying a per-minute rate, and as soon as the show ends (or if you decide to stop it), you will be asked whether you want to save that show recording to your "My Collection". Hit “Save” and it will slip in your video gallery so that you can access and re-watch at any time.
Note that if the model starts a Private show, the recording of the public show will automatically stop.