S L G - state symbols. Everything around us is made up of one of these things - it's either a solid, liquid or gas and you can see on the wall here each has an abbreviation in brackets underneath it (s) for solid, liquid is (l), gas is (g) and 'aqueous' means something that is dissolved in water and the abbreviation for this is (aq).
Once a reaction is completed we can show in an equation whether something was a solid (s); (l) a liquid or (g) a gas.
For example: water - which symbol do you think would be added to the formula? Answer (l) because the picture shows water in a liquid form.
What about this next one (picture of ice)? Answer? Solid which means (s). The formula for water is the same in both instances but one has (l) and the other (s) because one is water and the other ice.
What about this one (picture of steam) - which one do you think (l), (s) or (g)? Answer is (g) for gas.
What about if we dissolve salt in water like in the picture? Answer is NaCl which is salt and the (aq) tells us that the salt has been dissolved in water.