This is one of the tags that can be added to Wiki articles to denote how closely it adheres to official sources published by Wizards of the Coast.
"Canonical Speculations" cover topics that expand on and try to refine the things we know from the books - how does a certain Dragonmarked House operate, what are the military tactics of the various nations, and so on. Things that we don't know for sure - because they aren't spelled out completely in the books - but which follow logically from canon material.
(Note: For the sake of convenience, we will assume that all material on the Wiki is Canonical Speculation unless mentioned otherwise, so adding this tag is not neccessary in most circumstances).
For more details, see the Eberron Wiki FAQ.