What is the Anti-Virus engine?

I checked what Anti-Virus engine I often see in anti-virus software introductions on the Internet. Write down:

It is to use the virus library carried by anti-virus software (which is often automatically upgraded), and compare it with some signatures on the files on the system. The same is the virus.

"Simply put, it's anti-virus software!
Scan engines are the main part of anti-virus software. They are used to search computer viruses. The virus database contains a virus "specimen". During scanning, the scanning engine "compares" the specimen in the virus database with all the files on your computer. If the scan engine meets the specimen characteristics, the scanned file is a virus." ---- From Baidu Q &.