It means you cook the pastry before adding any filling!
Put greaseproof paper over pastry, fill void with dried beans or something and stick in the oven with your eyes open. You may not have to do anything other than just stick the tray in though-don't think the bean thing is always necessarry.
if they have refreed to baking beans (on re-reading your Q I see they have) it's probably worth using them or soemthing similar. they do have a purpose-I'm just googling what!
thought so-it's to stop the pastry rising on the base. when they refer to baking beans they're ceramic things. I'll see what you can substitute-I did say dried beans, but not sure everyone has them in the house!
Actually you don't need any paper, beans or anything else for that matter. If you just prick the base of the base all over with a fine fork it stays just where it is!
The pricking method is not suitable where a liquid filling is to be used as for a custard tart.
A good tip for the greaseproof paper is to cut it to size and screw it up tightly. When it is unscrewed and placed in the tart, there won't be any sharp bits on the paper to break the pastry. This is especially important when using a sweet pastry as these tend to be softer in texture.