A number line is a straight, horizontal line used to visually represent numbers in a sequence, often with evenly spaced marks that correspond to integers. It's a useful tool in mathematics for showing relationships between numbers, comparing their values, or demonstrating operations like addition and subtraction.

Key points of a number line:

1. Origin: The center of the number line, often marked as 0, is called the origin. To the right of the origin, numbers are positive, and to the left, they are negative.

2. Positive and Negative Numbers: As you move to the right from 0, the values increase (1, 2, 3, ...), while moving to the left decreases the values (-1, -2, -3, ...).

3. Fractions and Decimals: Number lines can also represent fractions and decimals, which lie between the whole numbers.

4. Use in Operations: A number line is often used to visualize addition (moving to the right) and subtraction (moving to the left).

5. Absolute Value: The distance of any number from 0 on the number line is its absolute value. This distance is always positive, regardless of whether the number itself is positive or negative.

Would you like to explore any specific concepts related to number lines?

Here are some related questions:

1. How can you use a number line to solve addition or subtraction problems?
2. What is the role of a number line in understanding inequalities?
3. How can fractions and decimals be represented on a number line?
4. How do you compare two numbers using a number line?
5. How does a number line help in understanding absolute values?

Tip: When working with inequalities, shading a portion of the number line helps in visually understanding the solution.