A vector is a quantity that has both size and direction. Force is a vector, and so are velocity, acceleration and displacement. A scalar has size only. Mass, speed, distance and time are scalars. To describe a force fully you must give its size in newtons and the direction it acts.
A free body diagram shows all the forces acting on one object. The object is drawn on its own, as a simple box or dot. Each force is drawn as an arrow that starts on the object and points in the direction the force acts. The length of the arrow shows the size of the force, so a bigger force gets a longer arrow. Each arrow is labelled with the name of the force and its size in N.
Only forces on the object are drawn, not forces the object exerts on other things. A book at rest on a table has its weight of 5 N acting down. The table pushes up with a normal contact force. The book is not accelerating, so the forces are balanced.
