There are different forms of yeast :
- Fast-Acting Dried
Dried yeast needs to be activated (as specified on the packet) using warm water and sugar.
The fast-acting variety is used in bread machines, as it doesn't require any preparation before use. It is more expensive than the normal dried yeast.
Both types of dried yeast are available in sachets and in small tins. I much prefer the tins, as they are much cheaper, and the sachets don't have the correct amount for size loaves that I make (so I either waste a lot, or have half full sachets lying around). Only use sachets if you make bread very infrequently.