I find this extruding and merging stuff kind of complicated. I have to keep myself aware that whenever I extrude something then press [Esc], I don’t cancel the extruding but instead have the new vertex/vertices, edges and/or faces at the same position as the original ones.

Anyway, I used the default cube and extruded the left-top edge. This resulted in a new face with new edges and vertices above the cube (first image). Then I extruded the edge on top of that new face, and dragged it to the (lower) right-top of the cube, which created another face. But I realise this causes a little issue: I now have one double edge and two double vertices, which I selected on the second image. How do I deal with these? The last lecture was about merging double vertices, but I still find that a bit complicated. And I’m wondering but don’t know how to do this for edges.

I do realise I could’ve prevented this issue by, after the actions of image 1, selecting the right-top edge of the cube and the left-top edge of that new face and press F, which simply creates a new face and two edges. But in order to get more insight in how Blender and modelling works, I would like to know how to deal with my situation when I go the extruding way and end up with these extra vertices and edge.

EDIT: I also still find deleting edges/vertices/faces kind of complicated. I usually end up trying all of them. I just don’t really know what to expect what they do beforehand. I do try to prevent ending up with edges and vertices that don’t have a purpose/don’t form a face. It seems like the Removing Edges option usually results in that. But it is kinda time-consuming…

EDIT2: Also, what I find interesting but the lecture doesn’t talk about, is the following (which at least applies to the default cube, idk about other shapes):

- Extruding a vertex results in 1 vertex and 1 edge (a 1-dimensional shape/a line).
- Extruding an edge results in 2 vertices, 3 edges and 1 face (a 2-dimensional shape/a squared plane).
- Extruding a face results in 4 vertices, 8 edges and 5 faces (a 3-dimensional shape/a new cube!).

Correct me if I made any mistake here.

Also, is there anything interesting/deep that can be said about this?