You’re asking about perhaps the worst marketing conception in a while.
HBO Max is different from HBO Go and HBO Now.
HBO Go will apparently go away....but if you have HBO Go or HBO or HBO Now, you can watch HBO Max for no extra change which is good given that it is basically just HBO right now.
Eventually, in theory, it will become a Netflix-like service with movies, shows and original content. However, ATT runs the show so smart money says this falls off a cliff.
And DC Comics which looks to be the source of much of the new programming.ATT owns Warner Brothers which owns HBO, Cinemax, TNT, TBS, etc.