This page from the vCD 5.1 documentation shows the possible values of the status field for various entities. The current doc uses numerical values but the API also has a few spots where string values are returned instead. The reference you found from the 1.5 API includes some of them; I think as part of the 5.1 doc update the string values were dropped from the schema reference.
An entity in the vCloud API is very similar to the likewise-named notion in database modeling. Wikipedia provides a fair definition of the term from entity-relationship modeling:
An entity may be defined as a thing which is recognized as being capable of an independent existence and which can be uniquely identified.
The RESOLVED
(numerical value 1) state means that most of the parts of the entity are present, but it isn't fully constructed yet. You typically see it when uploading an OVF and all of the bits have be transferred to vCD but stuff is still happening in the background prior to it being usable.