Quotation marks, also called 'inverted commas', are of two types: single and double. British practice is normally to enclose quoted matter between single quotation marks, and to use double quotation marks for a quotation within a quotation:
The oceans absorb the sun's heat, transferring it to the atmosphere and distributing it around the world via the ever-moving ocean currents. This drives global weather patterns and acts as a heater in the winter and an air conditioner in the summer.
There are two types of ocean currents: surface currents and deep water currents. Primary forces such as solar heating and winds start ocean currents. Secondary forces, including gravity and the Coriolis force, direct where the current goes. These are some of the facts about ocean currents.