There are 2 types of pool sanitizers:
- stand-alone sanitizers
- co-sanitizers
As the name implies, a stand-alone sanitizer is a sanitizer that can sanitize pool water all by itself (with some assistance from shocking the pool on a routine basis). Some examples of stand-alone sanitizers are chlorine, bromine, and salt.
As the name implies, a co-sanitizer is a sanitizer that must be combined with chlorine - albeit in trace amounts - to sanitize pool water (with some further assistance from shocking the pool on a routine basis. Some examples of co-sanitizers include mineral-chlorination, ion-chlorination, and ozone.
A mineral generator is required to send minerals to the pool. A mineral generator works best when its minerals are combined with chlorine to sanitize pool water.
An ionizer is required to send ions to the pool. An ionizer works best when its ions are combined with chlorine to sanitize pool water.
An ozonator is required to send ozone to the pool. An ozonator works best when the ozone is combined with chlorine to sanitize pool water.
The co-sanitizers are collectively viable sanitizer options because they still use chlorine (which has a proven track record of success as a tenured pool water sanitizer) but the amount of chlorine being used is just a trace.
You can read the Pool Manual for additional information about sanitizing pool water and the various co-sanitizers that are available.