LastPass users can now access their password vault using the companion mobile app instead of their password. The master password will remain, although LastPass wants to phase it out in the long run.
In the future, users can using the mobile app to unlock their vault when using LastPass in their browser. This is the LastPass Authenticator app, not the LastPass app itself. Authenticator is a standalone app to generate totp two-step verification codes. Typically, LastPass users are required to enter their master password for authentication when restarting the browser or at least periodically. They also have to enter that password if they want to make a change to an account.
The new feature makes that unnecessary; users can then log in and agree via the Authenticator app. It can be secured with a fingerprint or a face scan, in addition to a PIN code. For desktop users, there is currently no option to use biometric login methods such as Windows Hello to unlock their vault.
LastPass says the master password will persist for now. In time, the company wants to phase this out and replace it with alternative login methods based on the FIDO2 standard for passwordless login. In addition to an authentication app, this is also possible with physical security keys, for example. The new authentication method applies to both paid and free users. Last year, LastPass limited its free subscriptions by only making the service available on one type of device. That does not apply to this, because users do not need the mobile app, but the free Authenticator.