If you have lots of small features (e.g. counties) and they each belong to a larger group (e.g. states) then you can use the dissolve tool in QGIS to combine them into bigger shapes. This works for any kind of vector geometry, so it could be polygons as in this video or it could be points or lines. In this video I show you how to use the dissolve tool to create a states layer from a counties layer. I hope you find it useful.

See my intro and intermediate QGIS courses for more: https://www.udemy.com/user/alasdairr...