1.36 understand that:  the universe is a large collection of billions of galaxies  a galaxy is a large collection of billions of stars  our solar system is in the Milky Way galaxy.

The universe contains many galaxies. Galaxies contain many stars, each star has a solar system. Our solar system is an a galaxy called the milky way.
This diagram sums up the order of the universe to give some sort of visual representation.

cosmology.net

1.34 describe the differences in the orbits of comets, moons and planets

They all have elliptical orbits.

Comets and planets go round a star; moons go round planets.

Comets have more elongated orbits.

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 field strength is how strongly something pulls an object towards it.
Earth has a higher gravitational field strength 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 field.
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.

1.31 describe elastic behaviour as the ability of a material to recover its original shape after the forces causing deformation have been removed.

Elastic behaviour is the way that when you stretch an object with this behaviour it will return to its origional shape after the forces stretching it stop stretching it. Eg when you stretch an elastic band and then let go it pings back to regains its original shape and size.
Note that if you stretch an elastic band to far it won't go back? this is because it as reached its elastic limit which, beyond this point, means it looses its elastic behaviour.

1.30 understand that the initial linear region of a force-extension graph is associated with Hooke’s law

A force extension graph shows how much a material stretches for the force applied. The initial linear region is the straight diagonal line showing a linear correlation between force and extension  meaning that they increase at the same rate. This is Hooke's law.
But at some point the graph will begin to curve, this is when an object reaches its elastic potential.

1.29 describe experiments to investigate how extension varies with applied force for helical springs, metal wires and rubber bands

The most common experiment for this goes like so:

• Attach a spring to a newton meter and measure its length
• Add a 50g weight and measure again
• continue to add another weight and take another measurement
• Do this up to 400g

by plotting a graph from the results from this you can see the extension increases with force; as each time a weight is added the spring gets longer.

1.28 understand that the upward forces on a light beam, supported at its ends, vary with the position of a heavy object placed on the beam

This means you need to understand that if you have say a plank of wood being held in balance by springs pushing up at the ends and you put a weight on the beam, the springs would have to exert more force as they need to equal the downward force.

In this diagram the up wards and downwards forces are the same. If a 10N weight were to be placed to the beam the trestles would have to increase their upwards force by 10N