Vertex loop selections let you select several vertices across a polygon mesh without having to select each vertex individually. For more information, see Polygon component loops and rings.
To select a vertex loop on a polygonal mesh
All the vertices along the same line are selected.
To select a partial vertex loop on a polygonal mesh
All the vertices between the two vertices are selected.
You can re-use vertices from previous loop selections as the first selected vertex of another loop selection. You can use this technique to select multi-directional vertex loops.