(1) Please refer to the following table for the differences between lines, rays and line segments:

(2) The relationship between them: both rays and line segments are parts of a straight line, and they are related to a straight line as a part and a whole.

(3) There are two methods to compare line segments: ① Measurement method, in which the relationship between the size of a line segment and its length is consistent, the length of a line segment is measured with a scale, and the size of a large number of line segments is compared by comparing their quantitative relationships; (2) superposition method, comparing the lengths of two line segments AB and CD, or moving them to the same straight line, so that one endpoint A and C coincide, and the other endpoint B and D fall on the same straight line AB. If D is outside the line segment AB, CD > ab; if D falls on the line segment AB, CD < ab.

When learning straight lines, rays and line segments, we must pay attention to their connections and differences. Common thinking misunderstandings when doing problems are:

(1) Only one capital letter is used to represent the straight line; (2) Two points determine a straight line, and after three points, it is considered that a straight line cannot be drawn; (3) It is considered that straight lines and rays have lengths and midpoints; (4) the directionality is not well grasped when extending the line segment; (5) The statement is inaccurate.

In the axiom of linear nature, we should also pay attention to:

(1) "Yes" means existence, "Unique" means uniqueness. (2) The axiom of straight line property can also be said as "two points determine a straight line". In life, it is necessary to nail two nails to stabilize the slats. (3) According to the axiom of straight line properties, two different straight lines cannot have two or more things in common.