Refresh rate is the rate at which the screen data is refreshed, the higher the numbers the faster it refreshes.
A monitor with 60Hz refresh rate will only be able to display upto 60fps in games, this can cause tearing if you'r getting higher than 60fps in a particular game. A 144Hz monitor will be able to display upto 144fps.
A TN panel generally lacks in wider viewing angles, the colors are fine though not good as IPS panel while IPS panel lacks in faster refresh rates & response time but excellents in better viewing angles
1ms response time means that a pixel requires 1ms time in transistion from grey to grey, the lesser is response time better is gaming experience.
G-SYNC is a solution that aims to eliminates screen tearing, VSync
input lag, and stutter. You need a G-SYNC enabled monitor, allowing G-SYNC to synchronize the monitor's refresh rate to the output of the GPU(fps), resulting in a tear-free, faster, smoother experience.