A deductible is the amount you pay yourself each year before your insurance kicks in.
A higher deductible generally results in a lower monthly premium. That's why they are recommended for people who don't go to the doctor frequently, and freelancers.
Let's say your plan has a €1200 deductible
This means that each year, you will have to pay your first €1200 of medical bills out of pocket. After that, you will be covered according to your policy.
The discounted short-term plan works a bit differently
It has a 10% deductible up to €500 per year. That means you pay 10% out of pocket for each bill. Once you've paid €500 out of pocket that year, you will be fully covered according to your policy.
Dental treatments don't fall under the deductible and are covered according to your policy.