We need glucose for our energy within our body. If we take on sugar really quickly and concentrated like in sweets we get insurgence of insulin to deal with the sugar and if we eat a lot of refined sugar this happens a lot and puts strain on our liver. All other foods also contain glucose but in safer forms and our body takes it out of the food and turns it into glusoce in liquid form to flow into our bloodstream which then takes it to the muscles to be stored as glycogen. When we exercise or move or need ot for anything else it is then converted back to glucose and taken to where the body needs it. GLucose is basically a fuel for our body but there good and bad forms. If we have too much bad glucose (sweets chocolates etc) it eventually becomes like putting diesel fuel in a petrol car and body starts to break down because of it (diabetes).