Knowing 1 look OLL means any OLL you can solve it in one algorithm
2look OLL is only a handful of algs (part of full OLL) where you do it in 2 "looks"
One look gets all edges oriented (if it isn't, and if if all edges are oriented then you can solve OLL in 1 look), and then the final "look" orients corners.
Then you ar eleft with PLL
2 Look PLL is solving PLL in 2 looks. Full PLL is 1 alg, faster obviously (same with OLL)
2 Look PLL first solvse the corners (permutes them into place). Then the final "look" permutes edges.
2Look OLL/PLL is slower then doing it in 1 step, but it is also much less algs to learn.
If you are serious about speedcubing at all then I'd recommend learning at least fulll PLL