A gram is a unit used to measure the mass (some of you call it weight - depends on which planet you're on - see 'weight') of a small object, like a bee can weigh about 5 grams (or 5g). You need 1000g to make 1 kilogram (or 1kg).

The grid method is a good way to do your multiplication sums, by drawing a grid so you can neatly multiply each bit of the number and then add it up all at the end, instead of trying to do the whole lot at once.