The expression "az + b" represents a linear equation in one variable, where "a" and "b" are constants, and "z" is the variable. The term "az" indicates that the variable "z" is multiplied by the constant "a," while "b" is added to this product. This form is commonly used in algebra to describe relationships between quantities. In this equation, "a" determines the slope of the line when graphed, indicating how steeply the line rises or falls. The constant "b" represents the y-intercept, which is the point where the line crosses the y-axis. Together, these components help define a straight line in the coordinate plane.