Often, Identity Management and Access Management are jointly referred, mainly because their two management worlds likely coexist in the same project or in the same environment.
The two topics are however completely different: each one has its own context, its own rules, its own best practices.
On the other hand, some products provide unorthodox implementations so it is indeed possible to do the same thing with both of them.
Tools and practices to keep identity data consistent and synchronized across repositories, data formats and models.
Systems, protocols and technologies supporting user authentication (how Users are let accessing a given system) and authorization (which capabilities each user owns on a given system).
From the definitions above, Identity Management and Access Management can be seen as complementary: very often, the data synchronized by the former are then used by the latter to provide its features - e.g. authentication and authorization.