Arc command is used to draw elliptical curves, hemispherical and half rounds on the drawings. It is very useful command for all types of drawings such as civil,mechanical and electrical drawings. To draw arc there are many ways in autocad. details are given below.
3 Point Arc :
It is the easiest way to draw an arc in autocad all versions. You just have to provide 3 basic points.
Start, Center, End.
To draw an arc there is one center point of circle which creates a one forth length of the circle. In this option you have to chose first starting point and chose further by given choices accordingly.

Start,Center,Angle and Length
These are same to use but direction of rotation is different.
Start,End,Angle and Direction
It is draw as same method but you have to chose only end point this time despite of center point.