Main AVs (aka the cop)
- Norton, Avira, ESET, Avast, Bit Defender, etc...
- the first line of defense of the system ,will have to protect it efficiently against malwares.
- must be run alone without interference from other security programs to insure optimal protection; it is why some of them will check if other security softs are present in the system and will ask to remove them (often true but sometimes it is just for marketing purpose or to avoid the support team to fix potential issues)
Companion AVs (aka the reinforcement)
-Emsisoft, Webroot, MBAM, Immunet, Kingsoft, Tiranium, etc..
- Designed (most often) to be run alongside full-fledge AVs to support them if they miss some malwares (no AVs are 100% efficient against all threats , even if Panda's CEO said its product does
)
- Some of them (Emsisoft, Webroot, Tiranium) are specifically designed and coded in their core to give the priority to the Main AV and will kick-in only if a malware is missed by it.
- the others are companion because the way they are implemented and their engine designed is made to not interfere with the Main AV.