how can I be sure which shoe fits which pedal?

This may be a question for the new riders forum, but...here goes...

I just bought a pair of Pearl Izumi Attack road shoes that have the three triangular-shaped holes on the sole. What is that called???

The pedals I'm looking at are the Shimano 105 SPD-SL or Speedplay light action. I'm pretty sure that the Shimano's fit the shoe, but how do I know about the Speedplays? The pedals look completely different...

Any recommendations for pedals for someone new to clipless??

This will help you out, at least with respect to the speedplays.

Shoe compatability

SPD cleats will not fit a three hole pattern shoe(unless the shoe is also SPD compatible. Look to see if there are two parallel cutouts running toe-heel). If the shoe only has the three holes and nothing else then it is not SPD compatible. As for the Speedplays, they will work with the three hole shoe. the pedals come with an adapter that has a three hole mounting system. the cleats then mount to this adapter.

hope this helps.