Visible light has wavelengths of around 400 nm to 700 nm and a frequency range of around 400 THz to 800 THz. This is the part of the electromagnetic spectrum which can be “seen” and distinguished optically by the human eye. When white light is passed through the prism it spreads into the seven colors of the visible light spectrum. The Sun is an example of a natural visible light source.
Although we are blind to many wavelengths of light (which may be visible to some animals), we have instruments in place to detect them. But our world is oriented entirely around visible light as we can perceive it easily.
Apart from the most obvious use for visible light (we use it to see), certain properties of light (like not being able to pass through solid walls, artificial lighting) make us extremely dependable on them. Nowadays we can use visible light as a means of communicating. Visible Light Communication (VLC) can be used as a means of mobile connection (with a certain amount of disregard for security) and for communication in areas like hospitals where WiFi and mobile phones are undesirable.