What's a reception room / parlor / parlour / drawing room?

Solution 1:

Reception room is the room of a hotel (but it could be other buildings too) used for parties and meetings.
Parlor is a dated word to mean a sitting room in a private house. Generally it means a room in a public building used to receive guests; it could also be a room in a convent.
Drawing room is a room in a large private house where guests are received.
Living room is a room in a house for everyday's (informal) usage.

Solution 2:

In the UK, a Reception room is a stock phrase used by estate agents (realtors) and the like in property descriptions.

Basically it means any reasonable-sized room downstairs available to receive a visitor in. Specifically excluding kitchens and dining rooms, plus other rooms plainly unsuitable, such as a cloakroom (downstairs toilet).

Most houses only have one, so it's normally only mentioned if the property is up-market enough to have two or more. In many such homes that I've been familiar with, one of the two (usually the one at the front) is kept far more tidy, and is rarely used as 'living space' by the occupants except when they actually do have visitors.

Hotels sometimes refer to reception rooms, but confusion with the main reception area/concourse means they tend to call them meeting/conference/dining/banqueting rooms/halls.