1.32 understand gravitational field strength, g, and recall that it is different on other planets and the moon from that on the Earth

Gravitational feild strength is how strongly something pulls an object towards it.
Earth has a higher gravitational feild strenght than the moon: on earth we are pulled down so much that we can jump only for a few seconds; on the moon the time you can jump for is longer as it is pulling you back in with a weaker gravitational feild.
The reason for this difference is mass, the earth has more mass than the moon and so has a bigger gravitational field strength. Bigger planets than earth will have a higher gravitational field strength.