NameSilo's help pages lay it out day by day. For days 1 to 4 the domain stops working and the owner can renew at the normal price. On day 5 it is listed in the NameSilo expired domain auction, and the owner can still renew right up to the end of grace, which cancels the auction. From about day 34 to day 64 the name is in redemption, where only the owner can restore it for $75. Days 65 to 69 are pending delete, and around day 70 the name is released.
The detail that matters for a buyer: at NameSilo the market gets two chances at a name. First the auction, open to anyone with an account, then the public drop for whatever the auction did not sell. A backorder only plays in the second round, so the names you catch are the ones nobody bid on, which is often where a careful scorer finds the bargains.