Is Canon PowerShot G7 a Digital SLR camera?

no
but it is as good as one

No, it's not. You should check out this link. It talks about the difference between a compact camera and an SLR.

The G7 is not an SLR since it does not have a mirror that flips up to expose the sensor to light.

no, it isn't a dSLR.

you can find out more about this G7 camera here :
http://asia.cnet.com/reviews/digitalcame...

i am also new to dSLRs but i have since found out the differences :

1) a dSLR consists of a camera body and a separate lens which you attach to the body - as such, you can attach a variety of lens to your camera body so long it is supported.

2) the dSLR cannot zoom/unzoom the lens automatically like a compact digital, you can to rotate the lens manually.

3) most digital compact cameras can record movies but this cannot be done on a dSLR.

4) lastly, this is hard to believe and get used to initially, but you cant take photos using the lcd as a live preview - you have to use the view finder, and it is troublesome if you are wearing specs ...

Hope this helps a little :)