Antivirus software (or anti-virus software) aims to prevent access to computer systems by unwanted computer malware.  Viruses, worms or trojan horses can be used by criminals or mischievous people (called 'hackers'). They can be used to steal information or damage system files. If no antivirus software is installed on a computer, hackers may be able to access the information in the computer.

Types
There are many different types of antivirus software, and many antivirus programs can be downloaded for free. These free versions usually have some features missing, and the missing features are only available to those who buy the 
full version. Even still, many free antiviruses today have excellent virus scanning capabilities and can give people suitable internet security protections without the need to purchase additional protections.

Features
Antivirus software protects computers in many different ways. For starters, most antiviruses offer more than just "virus" protection. They protect computers from all different kinds of malware, like spyware, rootkits, phishing, and ransomware. For this reason, antiviruses are frequently interchangeably referred to as "anti-malware" programs. There are a few different ways that antiviruses protect against malware, but the most common way is through a regular scan of all the data and files on a computer's hard disk. In an antivirus scan, the software will look through every file on a computer, and it will compare each computer file's genetic makeup with the genetic makeup of already-known viruses. If a file has the same genetic makeup as a known piece of malware, it will be flagged as a problem. This is known as signature-based detection, and it is only effective when a malware file has been previously identified and shared with the community of malware researchers who maintain the malware database. Another typical kind of malware detection is through behavior analysis. This is when the antivirus software identifies an abnormal behavior in a computer file or program, causing the antivirus to flag that issue and assess whether or not the abnormality has been caused by malware or by something else.

Problems with antivirus software 
Most tests and experts claim that while antivirus software is extremely useful in preventing some cyber attacks, it is unable to prevent all attacks. That's because once a piece of malware has been identified, hackers know that this malware will be added to the list of already-known viruses, and it will no longer be able to pass through most signature-based detection systems. Also, antivirus software is not perfect, and there are constantly new and emerging threats that frequently bypass a computer's defenses.

Installing more than one antivirus is not a good idea. The two different antivirus software may interfere with each other and causes conflict.

Sometimes antivirus software sees viruses in files that do not really have viruses. This is called a false positive.  The antivirus software will sometimes remove files from the computer that should not be removed. This may cause other programs to not work properly.

References 

5.https://techrisings.blogspot.com/2020/11/SAntivirus%20removal.html

Software