Last Layer methods
The Last Layer (normally abbrevated as LL) is the layer that must be solved on a cube when all of the other layers have already been finished, normally assumed to refer to the U layer. Thus any last layer steps will be the last few steps of a method. The last layer is very often found with a prefix that refers to what part of the last layer is being solved in the particular method, such OLL (orienting the pieces), PLL (permuting the pieces), or CxLL (solving the corners).
There is no practical method that solves a completely scrambled last layer in one step every time, because there are far too many cases to learn (although the ZBLL method, which solves the last layer when edges are already oriented, is close to this level of difficulty): not counting inverses or mirrored positions, there are a total of 1,211 cases. Because of this, the last layer is always solved in multiple steps. The number of steps is counted in numbers of looks (the number of separate algorithms needed to finish the cube). The vast majority of speedcubers today use a two-look last layer (2LLL): possible ways to do this include OLL/PLL and CLL/ELL. Number of looks for the Last Layer is most of time between 2 and 4 (2LLL, 3LLL, 4LLL). Some cubers know a few 1LLL algs, but some softwares may know all of them. 5LLL and more are almost hardly ever used.