Help on INTRUSIONS & EXTRUSIONS IN ROCK LAYERS

Intrusions found in rock layers mean that the intrusion is younger than than the rock layers around it and the rock layers are older than the intrusion. How about extrusions? Is it YOUNGER than the rock layer directly below it, or OLDER?

"Extrusions are always YOUNGER than the rock it is sitting on."
https://docs.google.com/viewer?a=v&q=cac… (nice power point explanation)

Extrusive lava becomes rock, and starts to age as such, once it solidifies. So technically, extrusive volcanic rock is younger than the rock it overlies.