"Deductible" means the initial "out of pocket money" you must spend before an insurance company pays anything towards a claim. "Maximum Out-of-pocket expense limit" or "Stop Loss" is the maximum that can come out of your pocket during any claim.
You have to be careful with both. These deductibles can be "per claim" or "per year". In the case of medical insurance, the deductibles and stop losses are usually per year. That means that if a claim carries over into another fiscal year, you would incur yet another deductible and stop loss limit.
For example, let's say that your medical claims total out to be $25,000. If you have a $250.00 deductible and a $2,500.00 stop loss, the claim would be paid as follows:
The first $250.00 comes out of your pocket, leaving $24,750.00
If the contract is an 80% contract, then the insurance company would pay 80% of the $24,750.00 or $19,800.00 which would ordinarily leave you with a pocket expense of $5,200.00. But since you have a "Stop Loss" of $2,500.00, the insurance company would pay another $2,700.00 (depending on the contract). Sometimes, they would pick-up the deductible also.