This is a light overview of the Unity system, you can find a more in-depth tutorial made by the Unity team here: https://learn.unity.com/course/getting-started-with-unity
What is Unity?
Unity is a cross-platform game engine that allows for the of 3D, 2D, XR (VR & AR) products, such as games or animations.
Installing it on your system
Go to https://store.unity.com/#plans-individual and download Unity Hub. Unity Hub is a tool that allows you to manage your projects and the versions of unity that are installed on your system. The advantage to this is that you can have multiple versions of unity without having to worry about setting up your PATH environment variables (don’t worry if you are not familiar with these terms).
At the time this tutorial is being written, the Unity Hub program is at 2.3.2.