One needs a visa to enter a foreign country. But in Saudi Arabia, one needs a visa to both enter as well as get out of the country.
Once inside the country, an expatriate needs a so-called 'Exit / Re-entry visa' to go out and return to the kingdom. In other words, even if you have your passport and a ticket in your hands, you would not be able to get out of the country without an exit / re-entry visa. This could be quite a pain, particularly in case of a personal emergency when an expatriate wishes to leave the kingdom urgently.
There are 2 types of Exit / Re-entry visas - single and multiple. A single exit / re-entry visa is valid only once, i.e., for going out and returning. Once you return to the kingdom on a single visa, the validity is cancelled and you have to obtain a fresh Exit / Re-entry visa for your next trip out of the kingdom. On the other hand, a multiple exit / re-entry visa is valid for traveling any number of times back and forth out of and into the kingdom, but is valid only for 6 months from the date of first exit out of the country. In both cases, i.e., single as well as multiple visas, the sponsor's consent is required. In other words, your sponsor can actually decide when you can go out and re-enter the kingdom.
A single visa costs SR200. You are supposed to leave the kingdom within 30 days of the date of stamping and return before the date specified on the visa. Again, this is left to the discretion of your sponsor whether to apply for a validity of 1 month or 1 year 8- Usually, exit / re-entry visas are never given for more than a year.
A multiple visa costs SR500. The advantage is that once you have the passport and the ticket in your hands, you are free to go out of the kingdom and return within 6 months from the date of first departure. However, your sponsor's consent is required for this too for applying a multiple visa.
Most expatriates prefer to hold a multiple visa and prefer to pay the difference of their entitlement and requirement. That is, if the contract says that an annual vacation is your entitlement, and if you require a multiple visa, then you pay the balance of SR300 to get it, provided of course your sponsor agrees to the same.