[current]

There is always just one [current] revision. It is possible to have no [current] revision when a new object has never been unlocked. In that case there is an [in development] revision, but no [current] revision.
The [current] revision can be regarded as the most recent public version of the object. As soon as an object gets unlocked, the last saved working copy automatically loses its [in development] status and becomes the [current] revision. Conversely, if you lock a document (via Edit) you always lock the [current] revision.
So in the file system view of the ITP/MDK Repository, what we referred to as 'object', actually was 'the [current] revision of the object'. Everything you read there is still valid, if you keep this in mind.