Shoulder Dislocation is the term that is often thrown around for any disruption to the shoulder area.  However, technically this is not true as a dislocated shoulder refers more to the joint that is the glenohumeral joint. When the arm bone comes out of the fossa (socket) this is technically a shoulder dislocation. 

Injury to the Acromio-Clavicular joint is slightly different and technically is termed a Separated Shoulder.  It is usually the dislocation of this ‘strut’ that lies over the top of the actual ball and socket joint (glenohumeral) which is the shoulder articulation.  The AC Joint is particularly indicated when you have a fall or impact to the area.  And just to make more use of the anagram (or ‘I’m rather clever speak’) the term coined is FOOSH (Fall On OutStretched Hand).