A line between points with the same pressure is called an isobar. They are generated from mean sea level and are measured in millibars (mb).
Isobars are important to understand differences in air pressure. In the example on the right the pressure between te lines is higher than 988mb and lower than 992mb. The higher the differences and the smaller the spaces between isobars, the stronger the wind is. The wind moves from the high pressure isobar to the low pressure isobar.

For example: If you change the bottom 992mb by 998mb the wind blows harder, since there is more difference, thus air moves more quickly.
The same effect is being reached when you put the 992mb isobar line up. The difference might be the same, but the area is smaller, and wind blows harder.