Yeast

There are three different types of homebrewing yeast that come in countless different varieties. The two main yeast manufacturers are Wyeast and Whitelabs. Both of these are liquid yeasts, but they are a little different from each other. The last type is dry yeast. There are also numerous manufactorers of dry yeast.

Wyeast comes in two different packages. The first is the activator and the second is the propagator. The only difference between the two is size. The activator has 100 billion yeast cells where the propagator only has 25 billion. The way these work is there is a little package inside the foil cover and also some liquid. You break the inside package without opening the outer package. This releases the yeast into the liquid and after 4-6 hours the outer package will begin to swell. After it swells as large as possible you can pitch the yeast into your beer.
Whitelabs yeast comes in a vile. The only thing that you need to do is take it out of the refridgerator before you start your brew and when you are done just open up the vile and pitch the yeast into your fermenter. The vile contains 75-150 billion yeast cells.There are numerous manufacturers of dry yeast. These include Muntons, Coopers, BrewFerm, Safbrew, Safale, Lallemand, and many others. Dry yeast has been around for a long time where as liquid yeast is relatively new. Just open the package and pitch the yeast into the fermenter or rehydrate it in warm water prior to use. Both ways work just fine.

Each of these yeasts have their pros and cons. While the liquid yeasts are more expensive they also come in many different strains. If you go to Whitelabs yeast library there is over 50 different strains tailored to specific styles of beer. With dried yeast you are limited to maybe 10 different strains of yeast. I choose to use the liquid yeast. I have used both Wyeast and Whitelabs before and couldn't tell you what one is better. They both make great beer. The cost of liquid yeast can be offset. The yeast can be reused after the beer is transfered off the yeast. You can either clean the yeast and save it in a jar or just put your freshly brewed beer onto of the yeast leftover from your prior batch. Many people do this to get the yeast cell count up to brew higher gravity beer. They will start with a low alcohol content beer and work their way up to a barely wine which can be as high as 13%.