PLL or Permutation of the Last Layer is the fourth and last step of the CFOP method, which aims to permute the pieces of the last layer to have the 3x3 fully solved. This step is fully algorithmic, and consists of 21 cases.
Two look PLL is a smaller subset which orients the top layer in two stages. First, the corners are permuted - two cases, Then the edges are permuted - 4 cases.