The Universal Render Pipeline is still fairly new in terms of Unity. Lots of projects still use the Standard Render Pipeline, and some use the High Definition Render Pipeline. Previously the URP was the Light Weight Render Pipeline, but that was quickly changed, because essentially the URP is for everything, and the HDRP there if you want the absolute best possible graphics.
Since most projects will want to use URP, you may find you need to convert project to it. Fortunately this is fairly easy. You first have to install the URP package from the package manager.
With the package imported you can find a place in your project folder to create a URP settings asset, using Create->Rendering->Universal Render Pipeline->Pipeline Asset. This is needed for your project settings, where you can add it in to enable the new render mode.
Additionally, if you ever drop anything into your scene and the materials don’t load correctly, you might need to fix them using Edit->Render Pipeline->Universal Render Pipeline->Upgrade Project Materials to UniversalRP Materials. That should allow you to take most assets that might not be set up for URP by default and convert them over. Notably the assets you are using do need to support URP so if you’re downloading anything from the asset store, make sure it supports URP.