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.
Ocean currents are cohesive streams that circulate seawater throughout the oceans of the world. These currents may be divided into two categories: surface currents, which are driven largely by wind, and deep water currents, which are influenced more heavily by temperature variations and differences in water salinity.