CERN normally offers fixed-term employment contracts that last for 5 years with an option to extend by 3 years. The staff positions can be found on CERN's recruitment pages.
The cryptic job reference (e.g. IT-CF-DCO-2021-4-LD) refers to where in the organization the job is (IT, Computer Facilities), what year the job is advertised, and "LD" (Limited Duration) at the end tells it that the post has a duration of 5 years. To be able to apply, you need to meet certain preconditions, such as being a Norwegian citizen (or from another member state) and have good English skills (French language skills is an advantage, but absolutely not necessary)
Entry grade 4 or 5 for engineers with a bachelor degree, and 5 or 6 for engineers with a master degree or equivalent. With experience, the grade/salary goes up, and you get a supplement if you have a family. There are 40 working hours per week and six weeks holiday + 2 weeks Christmas holiday. Further, they offer 1.5 home trips a year covered for the whole family and excellent pension and insurance schemes.
If you have more questions, feel free to send them to Ole.Petter.Nordahl@cern.ch