CMS is the management of digital content through software or programs.
That doesn’t explain anything to someone who doesn’t speak tech. So, think of CMS as your Facebook account: you create a page, invite your friends, post pictures, status updates, comment on others pictures or updates.
Page creation: you are creating a place to view and manage specific digital content. Web content management (WCM) is for client-side or for a work place collaboration, enterprise content management (ECM).
Invite your friends: WCM ‘friends’ would be anyone the client grants access to update the website, including yourself. ECM ‘friends’ would be people needing access to any part of a group project or task that is digital. Access can be limited to certain parts of the website/project, depending on how the CMS is setup.
Post pictures/status updates and commenting: CMS will allow your ‘friends’ to post files, pictures, and other digital content to areas/portions they have been granted access. Access should only be granted for the portion of the project/website the individual needs to complete their task.
WCM allows them to have access to the webpage, change pictures and update content without the need to know or understand coding. ECM allows collaboration among the team members to create and work on different portions of the project.
This is my understanding, please leave a nice comment if I need correcting.