Air traffic control (ATC) can issue a standard terminal arrival route (STAR) to aircraft entering the terminal environment. The STAR usually communicates a predefined route of flight (fix1, fix2, fix3, etc.). The STAR procedure usually includes altitudes too. What will I hear from a controller when I am to follow the vertical guidance on the STAR vs. waiting for assigned altitudes?
In the U.S., the phrase "Descend via the (arrival)" means that you are cleared to the altitudes as published. Without that phrase, simply cleared for the ___ arrival, then your clearance is the fixes, but ATC will assign your altitude explicitly. In this case, the published altitudes may later be assigned, so descent planning should still be based on making the next fix at its altitude. You just don't go below your assigned altitude until cleared lower.
FAA Explanations: Starting on page 8 for "descend via" clearances: http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs400/afs470/pbn/media/rnav1_rnp1_rnav2/climb_descend_via_faq.pdf
ICAO phraseology has the same phraseology for being cleared for arrivals:
.724 Freigaben auf Einflugstrecken Clearances on a STAR G: DESCEND VIA (designator) (level) G: DESCEND VIA (designator) (level) CANCEL LEVEL / SPEED RESTRICTION(S) *AT (significant point)*
The phraseology for transitions is different from this:
RNAV phraseologies G: CLEARED (designator) TRANSITION G: CLEARED (designator) TRANSITION AND PROFILE
The interesting part about STARs however is: Even when cleared to descend to a flight level or altitude after previously being assigned a STAR, the altitude restrictions of the STAR are in effect until cancelled by the air traffic control unit, as referenced above, e.g.:
The waypoint EXMPL has a lower restriction (minimum restrictions of FL100) and you are cleared to descend via the STAR to FL70, the fix still needs to crossed at or above FL100, unless that restriction is cancelled with above phraseology.