Bahrain's phone system is GSM based like most of Europe. There are now three mobile carriers: "Viva" (aka Saudi Telecom / STC),  "Zain" (previously MTC Vodafone) and Batelco. Batelco being the more established are probably the better bet if you wish to use your international phone to roam.

If you are given a number (eight digits) to dial in Bahrain, a prefix of 17 or 77 means a landline, and a prefix of 3x (e.g. 32-39) designates a mobile line (previously you could identify each carrier by its prefix, but since the law allowing customer to switch carriers was introduced, this has become hard to do.)

There are no area codes per se, so to call a Bahrain number from outside, merely prefix +973- to the 8 digit number.