Inside or outside of Termux, it allows you to interact with your android device in general from the comfort of your main computer/laptop over ADB.
It becomes a super multiplier for Termux when I don't want to deal with the hassle of connecting a separate keyboard to my android phone/tablet.
(A heads up, I have to use the `--render-driver=software` switch in order for scrcpy to work at all on my laptop.)