flouts

Hi! I am building a web site with php and i have a drop down menu with 4 different music categories in a frame at the left of the page.When u click an option a page opens in the main frame dispklaying all entries found in the db for the specific category. As you understand the same query runs for all 4 categories and i want to create 1 page where i get a value from the drop down menu and pass it as a parameter to the SQL query. I understand this must be done with post and get variables somehow but i dont know how to use them. Somebody help?