From BlenderWiki

Mesh Editing

You found selection in meshes was quite a large and complex topic? Well, wait to see the editing part! Blender is heavily fit out for mesh editing, with many different tools, some of them very advanced and powerful.

All these tools may be found in one or more of three major places: the Mesh Tools panel of the Editing context (F9), the Mesh menu of the 3D views header, and the “specials” menus (W for Specials, CtrlV for Vertex Specials, CtrlE for Edge Specials, and CtrlF for Face Specials).

First, we will see the basics of editing, i.e. moving/scaling/rotating/adding/deleting vertices/edges/faces… These very low-level tools are most useful, but you will quickly want more advanced things. So next, we will see some tools dedicated to vertices, edges and faces.

From there, you will dive into several tools, more or less regrouped by type of actions:

• Deforming tools: they modify the location of vertices, without modifying the topology (i.e. not adding/removing vertices, edges or faces).
• Duplicating tools: they duplicate a part or the whole mesh, following different rules.
• Subdividing tools: they insert some vertices/edges/faces into the mesh.
• Miscellaneous tools: these are several tools, especially those not “externally” modifying meshes…

We will finish by two very high-level and powerful things: the retopo tool, that allow you to modify the topology of your mesh (i.e. the number of vertices, and the connections between them), and the Sculpt mode (and the related multi-resolution topic), which simply allows you to sculpt your mesh, as if it was made of clay!

Note that we regrouped here all tools that are quite specifically editing ones. There are other things that might also be considered as editing tools – but they are somewhat different, e.g. being non-destructive (like the modifiers), or of wider use/scope, like vertex groups… There are also some modifiers, like the Boolean and Subsurf ones, that might be seen as editing tools.