Caffeine is a “status bar application able to temporarily prevent the activation of both the screensaver and the “sleep” power-saving mode.”
The developer also words it another way: –
Caffeine is a tiny cup of coffee that sits idly in your system tray waiting for you to click it. Once you do, it instantly fills up with fresh coffee – keeping your computer awake!
It’s a strangely cute idea that is, surprisingly, actually really useful. I have many applications that, when full screen, aren’t able to stop the screensaver being initiated.
Which get’s annoying.
Watching YouTube videos also doesn’t inhibit the screensaver, either, so rather than having to manually disable your screensaver or turning your ‘minutes-until-suspend‘ settings up really high, just brew some coffee for your desktop!
You can install it using the official PPA. This ensures that you’re up-to-date with the latest features.