1) It was an attempt to stop smuggling of sugar and molasses in the colonies by lowering it's tax. It was designed to make England get more money but the colonists ended up profiting more.
2) The purpose of lowering the tax on molasses was to induce importers to buy molasses from British colonies instead of smuggling it from competing French and Spanish colonies. The Sugar Act also increased enforcement of smuggling laws. They had a good idea, they just went too far with it.