The "Standard H" is a pattern of positions into which the gear shift lever of a manual transmission may be pushed or pulled in order to change the gears used to drive the vehicle forward. This layout is used by the vast majority of transmissions and runs top to bottom, left to right, like so:
1 3 5 1 3 R 1 3
| | | | | | | |
+--N--+ +--N--+ +-N-+
| | | | | | |
2 4 R 2 4 2 R
5 speed 4 speed 3 speed
N = Neutral R = Reverse
It's known as the Standard H because it is certainly the standard from which few deviate, and "H" because of the path of the shift lever. Sometimes the reverse gear position on the 4 speed is located right and down rather than right and up. There are many other patterns, but these are by far the most common.