Fugi is absolutely right.
If you want to know more exactly what and why, I'll try to explain it short with layman terms: With vertical synchronization (V-sync) on a finalized image is shown as many times in a second as the refresh rate says, limited to the refresh rate of your monitor. Think about a slide show, changing pictures 60 times a second. With V-sync off you unleash the power of your video card. Instead of showing full images you may see slices from several images at the same time because the monitor can't handle that much information. The frame rate would be high, though, showing what the video card would be capable of. That information is good when buying a faster monitor - no use to get a 144Hz one if your video card only goes to 75 FPS, or the other way around, a 100Hz monitor would still be bottlenecking your frame rates if your video card could run 200 FPS with ease.
Of course speed is not the only thing you can achieve with a powerful video card. You can use the power to show more details as well. Cranking all settings to the max may well sink your frame rates even on your current monitor. Same goes if you get a monitor with a higher resolution. 4K literally quadruplicates the load at 60Hz, at higher speeds on that resolution the multiplier is even higher.
[Edit] From your other post I noticed that you're a computer builder so you probably already knew all this. Maybe someone else may find it useful.