In most countries calls to a cell phone are charged much higher rates (often 10 times more) than calls to a landline. So logically, when calling a cell phone from abroad you pay more than you do for calling a landline in the same country.
There are several countries where this rule doesn't apply (USA, Canada, etc). However, in these countries both the person calling a cell phone and the one receiving it pay for the call, which is not the case for other countries where only the caller pays.
Countries where cell phone calls are charged higher rates do not use area codes for cellular numbers. Instead they use special codes available for all mobile numbers regardless of geographic location. This way mobile numbers are easily identifiable - this website provides such information for most countries.