VST stands for “Virtual Studio Technology”.
It’s all the programs-addons that you open with your daw (remember what daw is?) to “fix your mix”.
There are not standalone programs.
Every single program that you open with your daw such as compressors, equalizers, drums, guitar amps and so on are in VST format.
How do I use them?
You create a folder and you put all the vst files there. The vst files are .dll types.
I usually create a folder at C:\VST so I can easily remember and access it.
Then you open your daw, go to your settings and enter the path to your VST destination.
Your daw now knows where to search for your vst.
You can also check this video (HD & Fullscreen preferred):