It is the court confirming who has authority. For a house, that confirmation is what lets title move.
Probate is the process by which the court confirms a will is valid and that the person named has authority to deal with the estate. The document that comes out of it is a grant, and it is what third parties — banks, Land Titles, buyers' lawyers — rely on before they will act.
Whether a particular estate needs one, and which kind, is a legal question that depends on the will, the assets and how title was held. That determination belongs with an estate lawyer at the very start, because everything downstream is timed off it.
How title was registered matters enormously. Property held in joint tenancy typically passes to the surviving joint tenant outside the estate, which is why a surviving spouse can often deal with a home without waiting on a grant. Property held as tenants in common, or in a sole name, generally does not work that way.
Nobody should assume which applies. A title search settles it in minutes and is the first thing to do.
The practical effect is on timing, not on whether you can sell. Marketing, showings and negotiating an accepted offer can generally proceed while a grant is being obtained. Completion is the part that waits.
So the possession date is the term to be careful with. A date agreed to please a buyer, without checking where the grant actually is, is the single most common way an estate sale falls apart.
Nothing here replaces advice from an Alberta estate lawyer. The role of a REALTOR® in an estate sale is to handle the property competently and to keep the sale in step with the legal process — not to run the legal process.