There are many ways to select elements, and it depends on what mode you are in as to what selection tools are available. First we will go through these modes and after that a look is taken at basic selection tools.
A key issue in modelling is the necessity to add vertices in certain zones of the mesh, and this is often regarded as splitting, or adding, edges in a given region.
The Weight Paint Mode is used to create and modify Vertex Groups. A vertex may not only be a member of one or more Vertex Groups, but also may have a certain weight in each group. The weight symbolizes its influence on the result.