It's unfortunate that people in the IT and software industries love to make up acronyms as a smokescreen to keep us from realizing that there are actually relatively straightforward concepts behind the jargon.  Archie Hendryx puts forward this view in a recent blog post and aims to explain all these additonal *aaSes that we're seeing in cloud computing terminology right now.  If you have any knowledge of cloud computing, you probably already know what IaaS, PaaS, and SaaS are.  I won't bore you with those descriptions.  But here is a summary of some other contrived terms you might run into while navigating the cloud infoscape:

MaaS

Monitoring as a Service: Basically it's monitoring utilities and computer power provided to you via a managed cloud service offsite.

CaaS

Communication as a Service: VoIP, VPNs, PBX and Unified Communications provided through a managed cloud service offsite.

XaaS

‘anything as a service’: IT as a Service through hybrid Cloud computing (public and privet) and is a reference to either one or a combination of IaaS, PaaS, SaaS, MaaS, or CaaS.

Hope these descriptions, which can be found in greater detail on Archie Hendryx's blog, will help you penetrate the smokescreen of murky terminology.

Source: http://it.toolbox.com/blogs/sanman/cloudy-concepts-the-meaning-of-iaas-paas-saas-maas-caas-xaas-49113