1. The standard way that runways are named and referred to in aviation
Runway Numbering
The standard way that runways are named and referred to in aviation

2. Direction There are two systems of referring to direction
Points of the Compass
Degrees

3. The Older System (Points of the Compass)
In the early days of navigation (sailing ships) directions were referred to as “points of the compass”. A ship would steer, say, “West south west”.
As navigation got a bit more accurate more points were added, but to refer to a direction as “East south east by east” was getting a bit of a mouthful. A better system was needed.

4. Degrees
The more modern system was to use degrees starting at due north and calling that 0 degrees (it is also 360 degrees which, by convention is how it is normally spoken).
By moving clockwise around the scale East is 090 degrees (always add leading zeros), South is 180 degrees and West is 270 degrees.
This gives us, obviously, 360 possible directions rather that the 16 using points of the compass.

5. If we have a runway with a direction of 270 degrees we take away the last digit (in this case zero) and the runway is called “Runway 27” and the number “27” painted at the beginning of the runway.
If you use the same runway in the opposite direction it is obviously 180 degrees different in direction and in this case 090 degrees, so it would be called “Runway 09”.
In this way it is quite clear not only which runway is being used, but also which direction. By using only two digits it is also clear on the radio that it refers to a runway and not a navigational instruction to an aircraft which would be 3 digits.
One slightly confusing point is that the numbers are painted ant the beginning of the runway, so in this case “27” is painted at the eastern end of the west facing runway.

6. If a runway was pointing in the direction of 314 degrees (Which is almost North West) it would become Runway 31 and if used in the oposite direction (134 degrees) it is called Runway 31.
If, instead of 314 degrees it was aligned on 316 degrees it would be closer to 320 than 310 and it would be called Runway 32

7. In the case of some large airports there are two runways running parallel to each other. These will be referred to (in this example) as “Runway 27 Right” and “Runway 27 Left” and in addition to the painted numbers there will be a “L” or an “R” as appropriate.
If there are three parallel runways the centre one is called (in this instance) “Runway 27 Centre” and there will be a “C” painted below the number