Every rank has it's own pay rate, and there are sub-rates within a rank. I'll detail a Private for you as it's the lowest in the ranks:
When you join the Army you're a Private(Recruit)) aka a Pte(R). After you receive your QL3s (trades training) you become a Private(Basic) aka Pte(B). After 30 months in the Army (2 1/2 years from enlistment date) you're deemed a Private(Trained) aka Pte(T). While these levels of achievement themselves don't carry a monetary value, your years as a Private do however. Each year you elevate in incentive pay category. For a maximum of 3 years as a Private (other ranks have different incentive levels, some upwards of 8 years). Most soldiers do 4 years as a Private, and are then promoted to Corporal (which is a rank you automatically receive after 4 years of service provided you're not in ****). So for the first 3 years of being a Private you receive pay incentives, the fouth year, you don't, this is because once you hit 3 years as a Private, you can be advanced promoted to Corporal (a full year early) so by not offering a pay incentive, it forces Privates to work hard for advancement. Anyway, the pay guide for a Private is:
Tier 1 (Your first year) $2421/mn ($29,052/yr)
Tier 2 (Your second year) $2960/mn ($35,520/yr)
Tier 3 (Your third year) $3556/mn ($42,672/yr)
After tier 3, you're in your 3rd year as a Private, and your pay does not move until you hit Corporal where it goes up to $4069/mn ($48,828/yr). As I said above, each rank has multiple catergories of incentives. The rank of Captain has 8 for example.
Also one must remember Specialist Pay. Certain trades are deemed specialist trades, and therefore entitled to SpecPay. SpecPay only kicks in when you're a Corporal or above, but it's a hefty difference. Lets look at 3 Trades, and the pay rates for a Corporal in each:
Infantry Corporal: (Tier 1) - $4069/mn ($48,828/yr)
LCIS Tech Corporal: (Tier 1 w/ SpecPay 1) - $4386/mn ($52,632/yr)
Search and Rescue Corporal: (Tier 1 w/ SpecPay 2) - $4645/mn ($55,740/yr)
Big difference when you factor in the two spec pay rates.
Overseas, yes soldiers get paid more, and that's all depending on where they are, where they're living, if they're married, and what the danger level is. A soldier who is single, in Haiti, living in a modular tent with air conditioning, where this is little danger, will make far less overseas pay than a married man, in Afghanistan, in a tent, where there is a high danger level. Also while overseas soldiers do not pay taxes for the duration of their tour.