Notation often helps makes the designation of objects simpler and can assist representing concepts by adding conciseness.
Here are some of the notation conventions we will use in discussing both graphs in Cartesian coordinate planes and mapping diagrams.

Object
Cartesian Plane
Mapping Diagram
Numbers Vertical or Horizontal Lines
Lower case: $a,b,...$
Points on the Left or Right Axis
Lower case:$a,b,...$
Ordered pair of numbers
a,b
A Point
Pair of numbers: $(a,b)$

 An Arrow Numbers on Axes: $a, b$ Arrow: $$A Line Numbers on Axes: a, b line: [a,b] Point in Plane Bold face/ Upper case: \bf P = (p_1,p_2)  An Arrow Numbers on Axes: p_1,p_2 Arrow:$$ A Line Numbers on Axes: $p_1,p_2$ line: $[p_1,p_2]$
Arrow in Mapping Diagram
(vector)
A Point
$(v_1,v_2)$
Bold face/ Lower case:  $\bf v$ $= <v_1,v_2>$
Numbers on Axes:  $v_1,v_2$