The style involves repeating heavy geometrical patterns, usually using poured concrete for its main material. Usually the surface remains unfinished, leaving the impressions of the forms used to pour the concrete, usually wood - this leaves the impression of the grain on the exterior of the building.
Here's a picture of the Boston City Hall. If you have a creative mind, you can see influences here from Frank Lloyd Wright's very early Prairie styles in the repeated upper patterns, although FLW's patterns were often inspired by Japanese style, and used for natural light.
The other distinguishing feature of this style is that the utility of the building is shown on the outside. For example, you can tell where the Mayor's office is in the picture, or the City Council Chambers, etc, by looking at the OUTSIDE of the building.
The other major building associated with this style is the Hunstanton Secondary Modern School, in Norfolk. It is unique in that the water storage facilities for the school are prominently displayed on the outside of the structure, rather than being hid on the inside.
"But in its day (1949-54) it was revolutionary. A homage to the great German modernist architect Mies van der Rohe, its steel-frame construction with brick and glass panels was more like a factory. Wondering where to put the water tank on all those flat roofs, the Smithsons instead set it high on a freestanding tower like a heroic campanile."
Here is a picture of the school from the period:
While the style of this school doesn't match the pattern of main utilitarian spaces being visible from the outside, this building, designed by Smithson, is generally thought to belong to the Brutalist style because of its water tower.
I now return you to your regularly scheduled, time-wasting web surfing.