Post release content:
1) If you didn't choose to download it and can't disable out of it explicitly, it's free, and it was made by the game developers, it's a patch
2) If you chose to download it, you can disable it explicitly, and it was made by the game developers, it's DLC. You may or may not pay money for it.
3) If you chose to download it, you can disable it, it's free, and it was made by someone other than the game developers, it's a mod.
+1
If we are piling in definitions:
I personally also like to distinguish DLC and Expansions. There just a big enough gap with what expansions in the old days offered, and the small bits of content that became popular with DLCs I don't like to throw them both into one basket, as IMO they offer rather different experience. The easiest example is Firaxis - XCOM2s small DLCs being DLCs and War of the Chosen being an expansion, with how much content it offers and how it overhauls experience on a deep level, rather then just sprinkling content on top of the base game.
As to D:OS2, it got only one DLC and that's Sir Lora was and is on sale. It got patched several times though, unclusing Enhanced Edition that included enhancements made during development of the console port.
I rarely see see DLCs. D:OS2 Sir Lora isn't really that as I think it was pre-order bonus for console release with existing D:OS2 owners getting it for free), Witcher3 that released bunch of "free DLC" to keep player engagement leading up to paid DLC release, and similar thing happened with Deadfire. DLC release in those cases has been more of a marketing stunt, then anything else. There is really no reason to release new beards as a additional free download instead of just patching it into the game outside PR.
