I was born in America and even I dont really know, we dont say trousers here. In The UK I guess pants are underpants or underwear and trousers are normal long leg wear.

Although Colton says he doesn't know the difference, in fact he does. In British English, the two are very different - pants are underwear while trousers are outerwear. A business suit, for example, consists of trousers and a jacket. In US English, the distinction is not so clear. The usual American equivalent of the British use of 'trousers' is 'pants' - so in US English, a suit would be composed of a jacket and pants. ( This conjures up an amusing image for a British person unaware of the American usage - as if someone had forgotten to dress properly and was going to work in his underwear!). The word 'trousers' is occasionally used by American English speakers to refer to a particular type of formal tailored 'pants'.

This, of course, still leaves you with the problem of how to understand and use these words. Sometimes, the easiest thing is to check whether the speaker or writer is British or American - this will tell you whether the 'pants' someone is referring to are underwear or outerwear. And which should you use? Well, in most cases I usually advise people to use the AE term if they're not sure who their audience is - for example, the American terms 'apartment' 'elevator' and 'movie' are generally better choices than 'flat', 'lift' and 'film' because they are unambiguous and universally used and understood However, in this case, ''trousers' might be a better choice, simply because 'pants' may be misunderstood. If you say 'trousers', then at least this is unambiguous. It isn't a word which an American English speaker would necessarily use, but they would at least understand what you meant.