Question
What is the difference between potting soil and potting mix?

Answer
Hi Tori, The word "soil" implies that there actually is soil in the bag.  Soil is decomposed organic matter.  It could be from decomposed bark, peat, leaf mold, any number of things that make up soil. "Mix" implies that it is a blend of things suitable to grow plants in.  Usually this is peat moss, perlite or vermiculite, possibly bark but no decomposed matter.
"Mixes" are usually light weight blends suitable for hanging baskets, window planters and container plants. They are great annuals and seasonal color.
"Soils" usually are heavier and are better suited for very tall woody plants that need the weight to keep them from falling over.  Soils have smaller particles and retain moisture longer than mixes.
Which one to choose should be based on the requirements of the plant you're wanting to grow.  Jim