An Introduction to ProBuilder
ProBuilder is an extremely useful built-in Unity package that lets you build, edit, and texture custom geometry. It is often described as a hybrid tool for 3D modeling and level design, optimized for building simple meshes but capable of detailed editing and UV unwrapping too. ProBuilder is great for in-scene level design, quick prototyping of structures, terrain features, vehicles, and weapons, as well as custom collision geometry, trigger zones, or nav meshes. Whew! That's a lot of versatility.
ProBuilder also has advanced features that include UV editing, vertex coloring, and parametric shapes. You can also export your meshes to tweak them in any external 3D modeling suite (Blender, of course, being our first choice!).
As if all that wasn't enough, ProBuilder has its own Scripting API to let you take advantage of many of its features from your own C# scripts. Mamma mia (as all Earthlings say)!
ProBuilder vs. Blender
ProBuilder...