The new CBA that was agreed during the offseason set forth new rules for practice squads, designed to give teams more flexibility during the regular season.
Following the onset of the global pandemic, these changes were temporarily added to, giving teams an even greater number of options as they seek to address the challenges of a potential in-season breakout, but also to account for the fact that there may be more short-term injuries as a result of the truncated offseason.
Here's the crux of what we've been left with:
Practice squads can be 16 players instead of the 12 it was going to be under the new rules. In theory, this could mean that a team who went into cutdown day with a full compliment of 80 players might only need to cut ties with 11 of them, assuming 16 of the other 27 cuts will clear waivers and go to the practice squad. (Of course, in practice, most teams will look to add players from around the league to both their active roster and practice squad).
Six of these players don't need to meet any eligibility criteria. The NFL has relaxed practice squad eligibility criteria in recent years and was going to move from the old system where all but two of the squad would need to meet complicated eligibility requirements that essentially amounted to not having played much in the NFL yet to a much more inclusive system. The CBA allowed teams to include six players that would otherwise have been ineligible of whom four must have no more than two accrued seasons. Now those six have no restrictions so you can stick a few older reserves that you otherwise would have cut onto the squad to give you an in-season option.
You can protect four players, but it's not exactly what it seems. Initially, this announcement seemed to give teams more flexibility to "stash" a young project who might not otherwise play (such as a draft pick who is a year away from contributing) without exposing them to waivers. However, this has instead been designed so teams can protect players at positions where they may be short in the week leading up the game. You allocate these four players to be protected every Tuesday, so Mondays can essentially be a free-for-all in terms of poaching from other team's practice squads and if you want to stash or fully protect someone, you'll still have to use a roster spot.
Up to two players can be temporarily elevated from the squad to the roster up to 90 minutes before kick-off. This creates a situation whereby a team can have 53, 54 or 55 players from which to choose their 48 active players for gameday. Those elevated players are entered into a strange kind of limbo where they are not actually under contract but they have a special addendum to their practice squad contract which ensures they get paid, have injury protections and are credited games as if they were on the roster, whether or not they are active for the game itself.
There are other restrictions and contingencies. The rules state that any player arriving from another team has to go through full Covid-19 protocols before they can even practice, even if they were cleared with their old club. This again makes it more likely that a team with a short term need will lean on their practice squad rather than bringing someone new in who won't be able to join them straight away. There are also roster exemptions and emergency spots available in the event of an in-season outbreak.
It's worth bearing these things in mind because it looks like the bottom end of every team's roster is going to be a fluid situation all year. The way things have been set up, we'd expect a lot of players who are released from the roster to still end up being required to play a role at some later point.