You feel cold when the temperature gets very low. It is cold in winter. The poor man in the picture is very cold, you can almost see him shivering. Ice and the inside of your fridge or freezer is cold. Airconditioners blow cold air during summer to keep you cool.
Something is cool if it is comfortably cold. The picture is of a cool drink.
Something that is popular, particularly with young people, can also be described as cool.
You feel hot when the temperature gets high. It is hot in summer. Fire is hot, and food or drink that is freshly cooked is hot. It is very painful to touch something that is very hot, and it can leave you with a nasty burn. The picture is of some hamburger patties being cooked on a hot grill.
