The Internet is millions of computers throughout the world, all connected by cables. In professional networking diagrams, the Internet is always displayed as a image besides. The cloud is a good analogy because just as a cloud is made up of millions of tiny water droplets, the Internet is made up of millions of computers.
You connect to the Internet through a device called a modem, and an ISP (Internet Service Provider). Your ISP might be TMnet, Jaring, Celcom Broadband, Maxis, or any of several hundred other companies.