Antivirus and antimalware software may be two separate applications but it is becoming more popular for them to both be integrated together in one application.
Antivirus and anti-malware applications are designed to detect malicious software running in memory of your computer. If malicious software is detected, the antivirus/anti-malware software will immediately attempt to block the software from running.
Antivirus/antimalware software can run scans in real-time and manually on demand. On demand scans will check all files on your computer for malicious signatures.
Modern antivirus/anti-malware software looks for malicious activity in order to detect malware. This is so that even if a virus has changed its source code (from which a signature is generated), antivirus/anti-malware will be able to detect it based on the actions the malware is performing. The malware doesn’t have to have a specific set of signatures in order for it to be detected.