The Shortage Occupation List is a list of all roles in the UK which UKVI believes there are not enough settled workers to fill. The current List can be found in the Immigration Rules here.
If a job is on the Shortage Occupation List, they will not need to meet the £25,600 salary threshold. Instead the threshold will be lowered to £20,480 per year and 80% of the going rate for the occupation, whichever is higher. Employers will find it more affordable to sponsor individuals in shortage occupations.