With broad match the Google Adwords system automatomatically runs your ads on relevant variations of your keywords, even if these terms aren't in yur keyword list. This feature is known as expanded broad match. Keyword variations can includ synonyms , singular/ plural forms, relevant variations of your keywords and phrases containing your keywords.

To find out how to see which terms your ads are actually being shown for, you will need to run a search query performance report. This report has only recently been added to the Google AdWords system.