Short answer
The subclass 186 Employer Nomination Scheme visa is a permanent employer-sponsored visa for workers nominated for genuine positions in Australia.
Subclass 186 is part of the Permanent Employer Sponsored Entry program. It allows an Australian employer to nominate a worker for a permanent position under the ENS program.
If approved, the visa is permanent. It also includes a travel facility allowing the holder to travel to and enter Australia for 5 years from the date of grant, so that travel period should be checked before publication if the page is updated later.