The lower the nm the more better people like intel can improve performance on as power consunption drops on idle and full load for same performance. Also companies like intel use this new nm to improve performance and add features architecture wise.
Anyway 22nm is the best yet by intel. Back in the olden days cpu's were like 350nm hence why computers were so slow back a couple of decades ago as they were huge so you could only get so little performance out of power consumption back then to now.
The smaller the nm, the more transistors meaning you can get big performance.