Document Service vs Mobile Documents and Mobile Services vs Mobile Secure

Hi gurus,

SAP HCP provides a lot of services and besides there are developed new ones. I am a little confused about two of them.

1. Document Services (or Document Repositories) on HCP vs. Mobile Documents (now accessed from HCP and also available via Mobile Secure(?)

2. Mobile Services on HCP vs. MobileSecure (MAM part)

What is exactly the difference between them? When should they be used, in which context?

I would appreciate some explanation.

Best regards

Beata