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... I also don't understand the difference, if any, between virus and malware.

There are no viruses that affect macOS, so just forget that idea.

Malware is anything considered malicious, which is subjective. Malicious software can simply interfere with a Mac's normal operation. It might for example prevent you from using the Mac as designed, or it might simply be poorly implemented by inept programmers. There is a lot of Mac malware whose developers do not consider them malware. Non-Apple "anti-virus" products are among them.

Longtime contributor Kurt Lang recently posted a comprehensive User Tip on the subject: What is malware? - Apple Community. I recommend it.

dougger wrote:

Is there any value to install AT&T antivirus plus on my MacBookPro? It is free through my AT&T internet. I also don't understand the difference, if any, between virus and malware. thanks

No there is no value. And third party antivirus apps may cause problems.

Effective defenses against malware and ot… - Apple Community

dougger wrote:

I also don't understand the difference, if any, between virus and malware.

A virus is a particular type of malware that works by spreading itself from one infected program to another.

The analogy is to biological viruses - such as common cold viruses – that reproduce by taking over cells in your body. By itself, a cold virus is an "inert" collection of genetic material. Once it gets inside one of your cells, that virus takes over the cell and turns it into a virus factory. Many new copies of the cold virus then flood out of the infected cell into the rest of your body where they may turn other cells into virus factories.

Eventually the infected cells die / are killed by your immune system (the normal case for common colds) - or YOU die (which can happen with nastier viruses like the ones that cause ebola).

A computer virus gets into your computer when you run something from an infected source. Once it has infected applications or other executable files on your computer, it tries to spread itself to other executable files whenever you run one of the infected applications. That is, it turns infected applications into virus factories.

Many other forms of malware just do something bad – possibly in a surreptitious fashion – without making a bunch of copies of themselves. Because they have different mechanisms, they have different names, but it doesn't mean that you want any of them on your computer.

I believe the most commonly accepted definitions of malware include all forms of intentionally malicious software, hence the name malware (a combination of "mal" from "malicious" and "ware" from "software").

Cisco – What is malware?

NIST Computer Security Resource Center – Glossary: Malware

This can include viruses, Trojan horses, spyware, password stealers, ransomware, software designed to vandalize a victim's computer, worms, some forms of adware, and so on, and so forth. I would also classify any software to display scam messages as malware. It is criminal or malicious intent that puts the "mal" in "malware."

Poorly implemented software is not, in and of itself, malware – although it is certainly possible for poorly implemented software to do as much harm to your data or your system settings as malware whose developers designed it to wreak havoc.

I'm not running out to install any anti-virus programs on my current Mac, but maybe that's just me.