Dynamic search for a website

I'm quite new to web developing but I'm trying to do some stuff by myself. However I'm currently "developing" a website for which I need something like a dynamic search. My data is stored on a db and for example if user chooses from drop down menus "fruit" and then "yellow" I want to search the db and output "banana".

I'm not sure how exactly should this happen. Can someone give me some advice on the logic of the whole process. Thanks in advance.