tangent is a line that touches the circle at one point going infintiely in both directions
chord is a line that goes from one side of the circle to the other and stays inside the circle, an example would be the diameter which is the longest chord in the circle
secant is a line that goes through the circle at 2 points, it's like a chord but it extends outside the circle
arc length is a section of the circumference
it's like the length of the crust when you cut a slice of pie or the crust of a pizza