If you have had experience with NATs via Cisco Routers or read about them in your CCNA studies, there are 3 Network Address Translation(NAT) types. Technically, two, see here, plus a third special case.
- Static NAT, one-to-one mapping
- Dynamic NAT, pool-to-pool mapping
- Dynamic NAT with PAT Overload, many-to-one mapping
So as you can see the two types are static NAT and Dynamic NAT, with the special case of Dynamic NAT with PAT overload.