Marketing is a broad category that encompasses many different things. The "Four P's" of marketing is a great place to start this explanation. Product, Place, Price, and Promotion are the most simple terms of understanding marketing. Here are some important jobs that are associated with each of the Four P's:
Getting informed on what you are trying to sell.
Explaining to outside parties what your product does.
Targeting the correct markets
Working to segment the total market
Researching customer perception of value
Looking into competitors pricing
Developing pricing strategies for your particular company
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Education: Since Marketing is such a broad category it is hard to say the exact amount of schooling a particular career would require. There are marketing bachelor (4 year) degrees available at Universities that would cover the majority of the options mentioned.