Active dry yeast is special prepared yeast in dry format, it contains about 6-8% moisture oppose to its counterpart fresh yeast which contains about 70% moisture/water. Dry active yeast is usually offered in different granules or small pellets. Dry active yeast also has a much longer shelf, typically 9-12 months depending on storage conditions. Fresh yeast has a shelf life of 2-3 weeks after products date. Although contrary to manufactures suggestion, I’ve used fresh yeast after 40 days and still got good performance. Another difference between dry and fresh yeast is that dry active yeast needs to be reconstituted, this is achieved by adding warm water ( 35-40C) to the dry yeast and dissolving it, letting it stand for a few minutes so that it activates. Instant dry yeast is similar to active dry yeast, the difference is that it can be added directly to the flour because granulation of the dry yeast is much smaller thus allowing it to dissolve on its own during the mixing process.