ONVIF (webcams)

ONVIF is an open industry forum that provides and promotes standardized interfaces for effective interoperability of IP-based physical security products.

In my experience it's mostly used for IP webcams, and allows for easy(er) integration of your IP cameras in your monitoring systems.

Now, Home Assistant is not a DVR and should not be used as one. You should look at other solutions if you want to record and store your security footage. But Home Assistant can be used to view your live feeds, check the camera sensors and such amenities.

Home Assistant has a native integration with ONVIF here. So you need to load and enable it, then add the cameras. It will scan your network for ONVIF devices automatically and will let you connect to them easily.