As Kim said: his American-British English glossary was correct on this, as I can testify from first-hand experience.

Stands are tiered seats at sports grounds, like bleachers. Stands are quite often covered (roofed), though, which bleachers are not, so strictly we should say "open-air stands".

They are not to be confused with terraces, which are tiered standing areas at football grounds in Britain, usually behind the goals.

See http://en.wikipedia.org/wiki/Terrace_(stadium)

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Note added at 26 mins (2011-09-29 22:36:18 GMT)
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On bleachers:
http://en.wikipedia.org/wiki/Bleachers

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Note added at 1 hr (2011-09-29 23:23:09 GMT)
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Can you have one bleacher? Here I'm hampered by not being American. Merriam-Webster defines a bleacher as:
"An often unroofed outdoor grandstand for seating spectators. Often used in the plural."
So perhaps you can indeed talk about a bleacher, but you don't usually. And apparently it is not impossible to have roofed bleachers; they don't have to be open-air. So perhaps we can omit "open-air" from our British equivalent. Though presumably they usually are open-air, because the name comes from being bleached in the sun.

I raise the singular/plural question because in British English you can and often do refer to a stand, in the singular. It means a section of tiered seating:

"stand
4 a large raised tiered structure for spectators, typically at a sporting venue"
http://oxforddictionaries.com/definition/stand

A sports ground of any size will have stands, plural, because it will have several sections of such seating. "Bleachers", however, can mean just one section of tiered seating. So its British definition should be "a stand or stands, normally open-air".