Dorian and MD pretty much covered it all.

90% of the difference is in the aircraft itself, only about 10% is service difference.

Air Canada has some 767's that are used on intercontinental routes, these have the much bigger space between the business class seats, and legrests on the seats, some have individual TV screens, etc.

They have other 767's (they look the same to me from the outside) that have all the business class seats squished together, no legrests, and smaller kitchens at the front of the plane.

The intercontinental 767's sometimes get used on domestic routes (mostly transcontinental but sometimes even Rapidair), but the domestic ones, with the squished together seats, may not be used on intercontinental routes, because the cargo compartment fire extinguishing system does not meet the rules for extended range operations over water. [Short answer - for ETOPS, the fire suppression system has to not only be able to extinguish the fire, but also to keep it extinguished for quite a long time - like, until the plane can find a suitable place to land].

Anyway, the domestic planes that have the seats all squished together are called "Executive" class, and the intercontinental planes with the space between the seats are called "Executive First".

I'm not sure about the new 340's and 330's - probably all of them are ETOPS - so I guess they also get more pitch between the business class seats, thus "Executive First" perhaps someone else can confirm this.

So far as service is concerned, on the intercontinental Executive First flights, the waitstaff serve the food from a cart that rolls down the aisle, and on the plain "Executive" class flights, the food is served on an individual tray, sort of like a TV dinner.

Food on Executive First is loaded the same way you would buy it at the grocery store - for example, the dessert cakes are whole cakes, the fruit salad comes in a big bowl, cheese comes in bulk - so it is possible to go to the kitchen later in the flight and get more (assuming you move quickly enough, before the front cabin staff send the leftovers to the rear galley for the back cabin staff to eat).

I don't fly domestic much, perhaps I have missed some of the finer points of the service procedures there.