Android Go is a lightweight version of the Android operating system. It is designed for entry-level phones with basic hardware components and less RAM available.
Android Go offers the "Go" versions of apps. For example instead of apps like Google, Files and Gallery, there are apps Google Go, Files Go, and Gallery Go.
The Android Go apps have some limitations, but because of that they have a lower hardware requirements, so they need less storage space and they use less RAM.
While Android 13 uses approx. 2 GB of RAM on phone startup, the Android Go 13 uses a couple of megabytes less.