I have been using GIS for a few years now (ArcGIS and MapInfo). But only when I have started using QGIS I come across OSGeo4W, as there is an option to download it on the QGIS website.

I have tried looking it up online but everything is very technical. I was hoping someone could explain in simple terms what it used for.

Also is there a difference between OSGeo4W / OSGeo?