Do I need to install Redis server if I want database cache?

I searched online and found that Redis is needed if I need database cache for my website. I found that I need three steps in order to use Redis for database cache of my WordPress site.
First step is to install Redis server, second step is install Redis php extension, third step is to use a plugin to enable Redis cache for my WordPress site.
For the second and third step, I can understand quite well, but for the first one, why do I need to install Redis sever?
When installing Hestia Control Panel, I have already installed Nginx.
After installing Redis server, will there be two servers on my VPS?