Not an aerospace engineer... but:

They are virtually interchangeable terms. when referring to the front wing on a airplane that has the main lifting surface to the rear and te horizontal stabilizer in front.

The term "Canard" actually refers to the whole aircraft, but is often used to refer to the horizontal stab on a Canard design. It means litereally "duck" in French... and was a descriptive of the apearance of one airplane in flight overhead. ("That looks like a duck"... someone who knows French translate completely... and you got what the guy said. The name stuck.)

Foreplane can also refer to the front wing in a design such as the "Quickie" where you get about equal lift from the front wing and the rear wing. (its an odd looking airplane... doesn't really fit the definition of a Canard.) There are about 4 or 5 model designs of this nature... only one full scale I have seen.