Many people on these forums are quite ignorant and do not fully understand the roles of major figures in the video game industry. I'm gonna help You understand these differences a bit more easily.

Developers are the people and places that actually make the game. They make all the engine graphic character plot nonsense and actually codes the game. A prime example would be Bungie Studios, Infinity Ward, and Treyarch. These developers are almost exactly like book writers.

The Publishers are the ones that take the game, publish it, advertise it, and make sure it gets on store shelves. More notable ones would be Activision, EA, and even major companies like Microsoft, Sony, and Nintendo (Sony not as much). These people are quite similar to the publishers in the book industry also. These people have very little say into what the game will be like, although they do give certain guidelines and deadlines.

There are also some companies which do both, like Nintendo (can't think of many others at the moment), but that's not really the subject here. If this helped anybody out, feel free the thank it or something like that. Thanks for reading!