Hollow Knight: Silksong is known to come for PC, Nintendo Switch and Xbox Game Pass already. Now, it is confirmed to also release for PlayStation 5 and PlayStation 4 at a future date, but before June 2023.
Steam page of Hollow Knight: Silksong says that players will be playing as Hornet, the princess-protector of Hallownest. You will be fighting your enemies while solving some puzzles in order to ascend on a pilgrimage towards the peak of the kingdom.
Hollow Knight: Silksong has a brand new kingdom, a lot of new enemies, and a new mode called Silk Soul. This mode is actually a new difficulty setting that changes the game very much after your first playthrough. In that regard, it is something like the usual new game plus mode.