There's plenty of variation in the use of the two terms but, in my regions of practice:
Grade beam: soil level beam transferring loads delivered by superstructure above, or expanding soil below, to discrete foundation elements (piles/footings).
Tie beam: soil level beam connecting two or more vertical load carrying elements -- usually columns -- for the purpose of stabilizing those elements laterally, particularly in the context of high seismic motion.
Often, you'll have grade beams around the perimeter of a building supporting the exterior walls and tie beams in the interior stabilizing isolated column foundations. When tie beams are required in the interior of a building, usually the perimeter grade beams will also serve as tie beams. And, of course, you sometimes have grade beams in the interior of a building as well to support interior bearing and shear walls etc.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.