What is difference between release and deployment?
From Wikipedia:


  Release management is the process of managing, planning, scheduling
  and controlling a software build through different stages and
  environments; including testing and deploying software releases.


Depending on the context the term release is used to reference either of:


the version of the software being released (from a version control system prospective)
the artifacts actually being delivered corresponding to that version (which can include physical media, printed documentation, etc)
the process leading to making those artifacts available and, in the case where the release includes deployment - deploying them in the respective environment (which may or may not be the production one)


Continuous Deployment (together with Continuous Integration and Continuous Delivery) is the modern DevOps methodology aiming to releasing better quality software as fast as possible.

So you can see Continuous Deployment being part of the release management in some cases, but you can also see release management without it - for example in the waterfall development model.

Related: How does continuous integration relate to continuous delivery / deployment?