Robyn:

Active dry yeast is little brown balls of dried yeast. the word active means it has to be activated.
to activate this yeast, the yeast must be dissolved in warm water (Approx 100 degrees F, if the water is above 115F it will kill the yeast). Once the yeast has dissolved add a small amount of sugar. (note: a solution of sugar greater than 10% slows down the yeast growth)when the water, yeast and sugar. start to froth(approx 10 mins) it should be added to the flour etc.

Regular Yeast in the baking industry means Compressed yeast which is wet yeast dried off and formed into a block and is a fawn colour

Fast yeast is a dried yeast that is very ACTIVE but is is not called active yeast. this yeast must be added to the flour and mixed dry through the flour. this yeast also contains ascorbic acid to compensate for the high level of dead yeast that are present in Fast yeast. Dead yeast has a reducing (softening) effect on the dough thats why they add ascorbic acid to counteract this effect.

Just a further note: Salt should never be added to the yeast solution directly as it has a retarding(slowing)effect on the yeast.

hope this helps.

regards.

bob