I agree that reading is your long term best bet, but in the short term, specialty grains are grains that are processed for special use in brewing. They are carmelized, roasted, toasted and burnt. These specialty grains then are used as additions to the base malt to create different styles. Pale ale will be made with roughly 90% base malt and 10% crystal/caramel malt, stout with 90% base malt and 10% of some combination of roasted, burnt, toasted and caramelized grains. These are just examples and don't truely reflect the percentages, but the point is that most beer's grain bill is mostly base malt, with a smaller percentage of specialty malts.