What happen if I use free sync monitor when I'm using a gtx 1060 3gb

Nothing special. It's just a monitor at that point, and you would want to buy it based on its other capabilities. Why? See below.

Both are vsync technologies. They work to try and solve a problem called 'tearing'. You have two main devices involved in graphics, your monitor, which draws them, and your card, which generates the data to be drawn. A typical monitor with no added benefits will be at a fixed FPS of 59, 60, or 144 frames per second (basically, your Hz ~~ Draw FPS for the monitor); a graphics card will just pump frames as quickly as possible. If those speeds do not match up nicely, tearing occurs - this is where the image from multiple frames is present at the same time, due to one device or the other generating data before a clean refresh of the drawing occurs. VSYNC is a software-based tech to try and fix this - it basically tries to cap your card at a matched rate to your monitor; but the trouble is that it's somewhat inconsistent.

How to solve this problem? Communication! If the monitor can order up frames as quickly as it can draw them, and the graphics card can explain to the monitor how quickly it can give it frames, the synchronization is perfect and no one of these interactions results in multiple frames being drawn or artifacted in a single operation, preventing the issue.

Imagine it's like helping people cross the street. If you're a good scout, you're not going to go speeding off with granny in your arms! You'll ask her and figure out what speed she's OK walking at. Now, if younger folks generally needed this assistance, you wouldn't want to walk slowly and hold them up... that defeats the purpose! So you ask, and they let you know how fast you can move. Perhaps some seniors are still sprightly and can keep up, or perhaps the younger fellow is missing a leg - everyone moves at different speeds, and the only way to help them effectively is to make sure everything is on the same page between the two participants. Everyone is happy that way.

FS and GS act to allow your graphics card to communicate with your monitor and try to better coordinate this drawing of frames so that your card generates them as needed and your monitor can draw them at the same rate; every frame is fresh and on time. Herein is the key benefit: if your card can't push frames in time, your monitor can dynamically slow its refresh rate to accommodate that; alternatively, if your monitor can only draw 60 FPS, the graphics card will be prepared to match that; rather than working with fixed numbers and hoping it works out like "dumb" monitors do.

However, because of how things have stacked up, they are mutually incompatible technologies; Freesync is known to generally be cheaper, but the trouble is that each of these technologies is exclusive (at present) to a particular graphics card company. Gsync works for NVIDIA based cards, such as yours, while Freesync works for AMD Radeon cards.

If you buy a monitor with the incompatible tech, it'll still work like a normal monitor. These additional benefits simply won't kick in.

What's better? Gsync, for you at least. There are mixed opinions on which one is best overall, but given that they're brand exclusive (AMD's an open standard... NVIDIA just refuses to use it, so effectively exclusive) the only one that's worth a thing to you is Gsync.

Don't care about what I said or it hasn't been a problem? Just get a normie monitor and save the money.