The general distinction
Canadian lottery and gambling winnings are generally not subject to income tax unless gambling winnings arise from carrying on a business. The facts of the activity matter.
Business activity can change treatment
The CRA explains that gambling activity may produce taxable business income or a business loss. Calling yourself a recreational player does not determine the result.
Income earned from winnings
Interest or other income earned after investing winnings may be taxable under its own rules. Keep gambling proceeds and later investment income distinct.
Cross-border situations need their own review
Foreign withholding and professional or business gambling require individualized advice. Consult the CRA guidance and a qualified tax adviser for your circumstances.