aft vs tail end

aft

• The stern portion of a vessel. 

• At, near, or towards the stern of a vessel (with the frame of reference within the vessel). 

• located at the back of a boat, ship, or airplane 

tail end

• The hindmost part of anything (a person, animal, or object), the rear end; the butt, buttocks; hindquarters, rump. 

• The last part of a period of time, event, or situation; the concluding or final part.