gglave

Yes.

Depending on the airline, the gate agent may want to check your passport and boarding pass at ORD before you board your flight to Vancouver. If you're on United they'll definitely want to do this, so as soon as you get to the gate go up to the counter and ask "Do you need to do a passport check?" If they say yes, hand them your documents.

In terms of Canada, you will need to fill out a customs landing card, and present it to the customs and immigration agent once you arrive in Vancouver. Usually they hand these out on the flight ("one per family") but if the flight doesn't have any, or the FAs forget, you can get them in the arrivals hall.

You show it to the officer with your passport and answer their questions, then they hand it back. You claim your baggage (if you have any) and then hand the card in as you exit the international arrivals hall.

Unlike in Europe, customs and immigration are handled by one person, so there's no "red line" / "green line."

When you fly back to the USA you will pre-clear US Customs and Immigration at YVR, so your flight back will be a 'domestic' flight, you don't need to go through customs and immigration when you land in the USA.