The Mullvad browser’s main goal is to make it harder for advertisers and other companies to track you across the internet. It does this by working to reduce your browser’s “fingerprint,” a term that describes all the metadata that sites can collect to uniquely identify your device. Your fingerprint can be made up of simple things, like what browser and operating system you’re using, to more invasive info, like what fonts and extensions you have installed, and what input / output devices your browser has access to.
It’s possible to configure a browser like FireFox, which Mullvad browser (and the Tor Browser) is based on, to have similar protections. However, doing so would require at least some level of technical savvy, as you have to know which switches to flip and have the confidence that you’ve caught everything.
According to Pavel Zoneff, a spokesperson for The Tor Project, Mullvad browser is very similar to the Tor Browser, it just connects to the internet through a VPN rather than the Tor network. (It doesn’t have to be Mullvad’s VPN either; if you use another service you trust, or if you have made your own then you can use that.) Mullvad browser also doesn’t offer the Tor browser’s censorship circumnavigation user experience, access to onion sites or services, or “circuit isolation and the integration with new-identity.” But again, if you don’t know what those things are, it’s probably not a huge concern.
See https://www.theverge.com/2023/4/3/23665477/mullvad-browser-tor-vpn-privacy-browser