There are many different types of grains used for brewing beer. The grains come from various types of cereal including barley, wheat and rice. They are used for many different applications in the brewing process, the most obvious being removing the fermentable sugars from crushed barley malt to provide the base of your beer, the wort. They are also used (among other things) for changing the colour, changing the flavour, improving head retention and increasing smoothness.
Below are some examples of the grains and their uses:
Pale Malt: This is the main ingredient used in cask ales and will be the biggest cost in your grain bill due to this.
Pilsner / Lager Malt: This looks very similar to pale malt but is the main ingredient used in lager style beers.
Crystal Malt: This is used to add colour and residual sweetness to your ales and is generally used in small amounts as part of your recipie.
Vienna Malt: This is used to improve flavour, colour and aroma. Just like crystal malt, it is added as in small amounts.
Amber Malt: This malt is used to add a dry biscuity finish to your beer.
Brown Malt: This is used in stouts and and porters to give tastes of coffee.
Chocolate Malt: These are used for adding red and black colours to your beers. They also add a nice roasted flavour.
Flaked Rice: This is used for increasing strength without overly affecting colour. Often used in lagers.
Flaked Barley: Used for increasing head retention, body and flavour. This has to be used carefully in lighter ales as it can make the beer cloudy, this is not an issue in dark beers.
Flaked Wheat: Used to aid foam production in a poured beer.