Brompton models come with a standard three digit acronym, which will tell you the handlebar type, the gearing, and whether or not the bike has mudguards and a rack. An example would be an S2L: S Type handlebars, two gears and mudguards.
There is a choice of four handlebar types: M, S, P, and H. Using the Our Bikes section of the website, you should be able to identify which handlebar type appears on your bike.
Details about the gearing options are available in the Gearing section; you should be able to tell how many gears you have by taking a look at the gear triggers (both of which are shown and explained on the gearing page).
The final letter at the end of the model acronym can either be E, L or R. If your bike has no mudguards it is an E version, if it has mudguards then it is an L version, and bikes with racks are R versions.