It's odd how often people put studios and publishers together, when the relations are (often) a lot less close than people on the outside realise.

In this case though I can sort of understand it. Activision has invaded the battle.net launcher which was long reserved only for blizzard games. CoD is now right next to WoW in their launcher.

Yet another reason to hate the proliferation of launchers ;)

For me being outside of thess relations are indeed it is not so clear. Can you describe it more ?

In the original terms, game studios/developers made games, game publishers provided financing and support (such as distribution and marketing) to game studios.

You can have hybrid entities, and you can have game studios/developers chose to self-publish, or whatever. The relationship between a publisher and studio can also vary. You can have one offs, where an independent game studio pitches a single game to a publisher, and they sign a deal for just that one game. Or you can have longer term relationships. For example, after Bungie re-spun out from Microsoft, they signed a 10 year deal with Activision (but they weren't owned by Activision). Or sometimes, publishers can straight up own game studios (they'll usually own a whole bunch of them). For example, Microsoft owns a whole pile of game studios (like recently acquired Bethesda).

Activision-Blizzard is the parent holding company. Activision is the game publisher arm, and Blizzard is a separate game studio arm. Call of Duty for example is developed by a family of studios (for example: Infinity Ward) that all (well, at least IW) operate as parts of Activision. Like any creative-ish field, the exact relationship between the creative types, and the money types is... always contentious?

Blizzard's relationship with Activision (the publisher) is different from say Activision's relationship with Infinity Ward in that Activision the publisher actually owns IW, while Blizzard is technically an equal business unit with Activision the publisher.