Yes and no.
Proxmox VE is build on Debian and Proxmox adds their stuff to that. Both need to be updated. If you look in the repositoryconfig (GUI or files) then there will be (3) Debian repositories and a (1) Proxmox repository. You need all these (4) to update your system. If you have no Proxmox repository configured only Debian will be updated.
Debian you dont have to touch they are probably ok. You only have to choose a Proxmox repository (Enterprise or No-subscription). The difference between these two should be clear by now (I hope).
If not (from the Admin Guide):
3.1.2. Proxmox VE Enterprise Repository
This is the default, stable, and recommended repository, available for all Proxmox VE subscription users. It contains the most stable packages and is suitable for production use. The pve-enterprise repository is enabled by default
3.1.3. Proxmox VE No-Subscription Repository
This is the recommended repository for testing and non-production use. Its packages are not as heavily tested and validated. You don’t need a subscription key to access the pve-no-subscription repository.