There are a lot of good explanations, but I think I can be more concise:

Universal health care is a healthcare system that's available to all, regardless of financial status. In Canada, our health system is administered by the Federal government (via the Canada Health Act), and funded through tax revenues.

Any Canadian (or more broadly, anyone that meets the residency requirements) is automatically covered, at no cost, for most (but not all) medical services.

Certain categories aren't included under the services outlined in the Canada Heath Act (dental and vision care, and prescription medications), but there are supplementary health plans available for those that ease the financial 'sting' a little.