An Insert Multi Mesh or better known as IMM, is a type of brush where you can collect not only one, but a large panel of meshes, ready to be inserted.
This makes it possible to have different thematic brushes with specific meshes such as screws, tubes, flowers or more. Then you can select your desired brush, followed by the specific insertion mesh and drag it on your model to insert. You can also change between insertion meshes without needing to select or load a new brush.
After selecting an IMM Brush, simply press the M key to display a floating box which lists all the available meshes within the brush. Then click on the shape of your choice.
Curve Mode can also be used together with the IMM Brushes.