If you look on the epriodic table then you'll see the atomic masses of elements. For example Hydrogen is 1, Carbon 12 and Oxygen 16. This means that 1g of Hydrogen is 1 mole and so id 12g of Carbon and 16g of Oxygen.
Like i said, i never did moles before sixth form. So if you let me know what kind of things you have to do that involve them, i can help you. But i don't want to ramble on about things that you don't need to know that might confuse you further.
As has been said above, its simply a unit of measurement for the number of particles. Moles are used because it would be impractical to talk about the number of atoms that react, as its normally trillions at a time. The mass of one mole of a molecule is equal to the relative molecular mass of the molecule, expressed in grams: for example water, H20, has a molar mass of 18g.
Each mole contains avogadros constant of particles in it. The amount of grams needed to equal avogadro's constant is, helpfully enough, the atomic mass of the element, in grams. Hence 12g of Carbon-12 is one mole.
Empirical formula is the simplest whole number ratio of elements in a compound. For example, molecular formula C6H12Cl2 simplifies down to C3H6Cl.