Corners markets price the number of corners: match totals (over/under 9.5 is the classic line), team totals and corner handicaps. Corner counts follow attacking volume and width of play — a dominant team funnelled wide by a low block generates corners regardless of the score.
The common mistake is treating corners as random garnish. They correlate with shots and territory, so the same reasoning that prices totals applies: teams that attack down the wings against packed defences run high counts, counter-attacking pairs run low ones.
Two teams averaging a combined 10.8 corners against similar opposition make over 9.5 roughly a 58% proposition — fair odds ~1.72. A price of 1.90 is value if the sample behind the average is honest; the same price is a trap coming off three atypically open games.