A face loop is a path of polygon faces that are connected in sequence by their shared edges. For example, if you select one face on a sphere, a loop selection selects all of the faces along the same line of latitude or longitude on the sphere by selecting each successive face that is adjacent to the selected face.
Face loop selections let you select several faces across a polygon mesh without having to select each face individually.

There are several options for selecting a face loop on a polygonal mesh in Maya. You can select:
To select a face loop on a polygonal mesh
over a polygon mesh and select Face from
the context sensitive marking menu.
+
double-click an adjacent face in the direction you want the face
loop.
To select a partial face loop on a polygonal mesh
over a polygon mesh and select Face from
the context sensitive marking menu.
+
double-click a non-adjacent face on the same line of longitude or
latitutde.