What is Malware? Does Comodo Scan for all types of Malware?

Definition of Malware: The term malware (short for malicious software) usually refers to any file that intentionally alters your computer (usually without your permission) in order to impair functionality, control your system, breach your privacy, advertise, or produce some other unwanted behavior. Malware is a general term that encompasses many types of malicious programs, including viruses, trojan horses (“trojans”), rogues, spyware, keyloggers, worms, rootkits, dialers, backdoors, etc. There is a good explanation of malware on wikipedia.

Does Comodo Scan for All Types of Malware? - Yes.
Currently, many scanning programs check for all types of malware regardless of the term used their name. For example, Comodo antivirus scans for all types of malware, even though its name is “antivirus”. Superantispyware checks for trojans, rootkits, rogues, keyloggers, spyware, etc. even though its name is “antispyware”.

How important is the number of definitions?
The number of malware definitions is not important. The important statistic is the detection rate.
When applied to malware, the terms “definition” and “signature” mean the same thing: a rule that detects one or more malware items. The number of definitions does NOT correlate with the number of detections. A single definition may detect hundreds or thousands of malware variants. Having fewer malware definitions (each of which detects more malware) allows an anti-malware program to use less resources (i.e. it applies fewer definitions to catch a given malware; thus, it is more efficient).
False positives have little to do with efficiency and more to do with accuracy. I define accuracy as “absence of errors.” So, a signature may be very efficient at detecting a given malware (e.g. it detects 95 of the 100 known variants), but it may not be accurate if it also detects 100 false positives.
So, it does not really matter how many definitions are present. It matters how well those definitions detect malware without generating false positives.