The general equation of a straight line is y = mx + c, where m is the gradient (slope), and y = c is the value where the line cuts the y-axis. The number c is called the intercept on the y-axis. The equation of a straight line with gradient m and intercept c on the y-axis is y = mx + c. Whichever way the line is presented, teachers will often say that it is good practice to write it in the format: y = mx + c
P.S. My experience is at primary level. I am not a secondary teacher, but I've learned some gems when helping my kids with their secondary school Maths.
