This video introduces the number line, and it explains what you need to know about those number line definitions in books that always begin with crazy phrases like "There exists a line with a correspondence between real numbers and..." Yikes!
Congruent Segments on the Number Line
This video covers the problems where you are given segments on a number line and you have to know if they're congruent or not.
Adding & Subtracting Using The Number Line
This video covers the absolutely most important thing you can do with a number line: addition and subtraction, especially when negative numbers are involved. People who can do math in their heads are all using this technique. Visually. In their minds. 7.NS.1, 7.NS.2, 7.NS.3
If you do not have an account, you should get one, because it is awesome! You can save a playlist for each test or each chapter, and save your "greatest hits" into a "watch right before the final" list (not that we recommend cramming, but when in Rome...)