Most of use know that @machin3io , the developer of this addon is the magician under the Blender addon developers. MACHIN3 developed some amazing, paid, addons like MESHmachine and DECALmachine, but this addon is free and there still maintained.
What does the addon do?
There is a lot the MACHIN3tools addon can do and it is very configurable in the preferences. Overal the addon is for functional purposes like working in the 3D view, Pie-menus but there are also features for editing like clean up mesh, smart vert, smart faces etc. If there is a feature you don’t like, you can turn it off in the preferences.
For who is the addon?
Well, because there are so many feature and it is very configurable, I think it can be an addon that is useful for anyone. As usual, an addon from MACHIN3 comes with excellent documentation which you can find here.