Copyright is important because it protects the interests of those who create and those who invest in creativity.
If there were no copyright, it would be impossible for creative people to make a living from their creativity. No one would be willing to come up with the money to make a film, to write or publish a book or journal, or to bring out a record - because there would be no way of earning a return on that investment. Now that it is so easy to copy material, it is more vital than ever that we respect copyright so that people continue to produce the creative works that society needs. This is why copyright law has a method for providing financial reward to creators for uses of their intellectual property.
The traditional method of recompensing the creator and/or the investor in creativity (normally the publisher) is to purchase a copy of the book or recording or take out a subscription to a journal. Some people, for a whole variety of reasons, do not always wish to do this. They may only want to read a single journal article or book chapter and feel that a subscription or purchase of the complete publication is simply not worth the cost. In response to this need, some publishers now sell single articles from their journals.
However, it is often much easier to obtain a copy via a supplier such as the British Library and in order not to deprive the author and publisher of income the law says that in many circumstances a copyright fee must be charged. (See below 'Are there occasions when a copyright fee is not necessary?' for circumstances in which a fee may not be charged.) If you pay the copyright fee, and abide by any terms and conditions associated with the provision of the article (for example, you cannot re-distribute or re-sell it because this would also deprive the author or publisher of income), you will not be in breach of copyright.