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.
Oceanography is important to study because the worlds oceans are critically important for sustaining life on Earth. Maintaining ecological balance in the words ocean helps insure we are keeping the worlds carbon levels in check. A large percentage of the worlds oxygen comes from the oceans.