Let’s start with the differences between “viruses” and “malware.” Viruses are a specific type of malware (designed to replicate and spread), while malware is a broad term used to describe all sorts of unwanted or malicious code. Malware can include viruses, spyware, adware, nagware, trojans, worms, and more. However, because viruses (and to a lesser extent, trojans and worms) made headlines a few years ago, most security companies focused their marketing on them, which is why they’re called “antivirus.”
Other tools call themselves “anti-malware,” but malware is a broad term that includes viruses—so it isn’t clear which threats they cover either.