Wellll.......
Its a radio signal so all sorts of stuff can interfere with them, so it can depend on whats happening at any given time or where you are using the laptop.
Prime culprits for interfering with wireless.... brick walls (!), microwaves, cordless phones, electrical wiring & bluetooth signals.
Also if you are using the windows wireless utility that can have problems, in that the signal drops every few minutes for a little while.
Main thing is, if its a constant problem, go into your router set up page and you can usually change the radio channel it transmits on (1-11), find one that works best.
I had to give up on wireless when i lived in a flat that was in a converted village courthouse/police station/police lockup, it had 3 foot thick stone walls all through and the wireless was useless. Most modern houses arent like that though lol.