In a buyers market, supply exceeds demands. Meaning, there are more houses for sale than people actively looking to buy a house. Characteristics of a buyers market include: buyers spending more time looking for homes, stable or even reduced prices, and buyers having more leverage when negotiating.
In a sellers market, the exact opposite holds true. Demand exceeds supply. Meaning, there are more active buyers than there are houses for sale. Characteristics of a sellers market include: homes selling quicker, possibility on multiple offers, and price increases.