Difference between Line and Polyline?

The Line and Poly line are two objects with difference properties in Auto-CAD. In the line command, every time we click, the part between two points are- an Independent unity but the part between the first point and the last point consist of multiple separated independent unities.

The Line command allows you to create single straight line or a chain of straight lines.

By using this command-

• We can make object where line is used.
• We can select one line among them to edit the drawing. However, In the poly line command- There is always a unity which cannot be separated. We can only operate the whole unity when executing attribute edition is done.
• With the Line command we can pick a start and end point and AutoCAD will draw a simple line connecting to 2 points. It can continue to pick points and AutoCAD will draw a straight line between the picked point and the previous point. Each line is an individual segment and can be modified independent of the other lines. 
• The POLYLINE command allows you to create “ground” objects that can be extruded, given line width on the screen, and can contain arc segments. In this command,
• We cannot give offset in single line. If we want to give offset in single line then firstly, we have to explode the poly line, and give the offset in single line. 
• The Poly line is clearly superior to the line and spline. It produces a joined line which is then easier to use for other functions like hatch boundaries and offsetting. It has the extra editing functionality of the multi-function grip. The poly line can provide all that the line and spline can – but without the associated inefficiencies. 

**For Example- In the specify object

• The Line specifies is only a part of it. While in the poly line it specifies the whole figure of drawing.
• The line command can only be used to draw lines and it is easy and simple to operate. " BUT " In the poly lines command, not only we can draw lines, but also we can draw arcs, besides we can add (Arc, Close, Length, Undo, Width)these options to the menu. 
• We can draw a poly line with changing - (Line weight and Arcs) 
• A poly line is just a series of line segments that are joined together to form a single object. 
• Line command can be use in 2D Drawings and Poly line command in 3D. 
• A rectangle created with the line command, consist of four separate entities. 
• In poly line command, A rectangle created with one continues poly-line would be treated as a single entity.

The distinction between line and poly line is-

LINE = 2D= OK

PLINE = 3D= OK

(CAN CONVERT POLYLINE BY COMMAND EXPLODE)

Therefore, If we use just  2D drafting will not have to use the poly line.