Figure 3.8 - Extrude in the Toolbar

Here are all the extrude types:

Extrude Region: Select one or multiple elements to extrude them

as a single block. That is the default extrude option you can trigger

with the E key.

Extrude Manifold: A powerful new extrude mode introduced with

Blender 2.9 that can automatically divide and erase faces based

on their location. It is a great tool to extrude to the interior of your

existing model.

Extrude Along Normals: The extrude will use the element

normals to get a direction. Usually, the normals go towards the

perpendicular direction from the selected element.