The things you own that are worth a lot of money and are small enough to carry away — jewellery, watches, cameras, laptops, passports, cash. It is a plural noun and it lives almost entirely in the world of safety and theft: hotel signs say 'please leave valuables at the front desk', gyms say 'do not leave valuables in the changing room', police say 'keep your valuables out of sight'. That is the natural home of the word, and if you learn it in that setting you will use it correctly. Notice what it does not usually cover: your house and your car are worth far more, but people don't call them valuables, because the word carries the idea of small, portable, easily stolen. Notice too that it means money-worth, not heart-worth. Your grandmother's letters may be precious to you, but they are not 'valuables' unless someone would pay for them.