As humans, we perceive the world in analog. Everything we see and hear is a continuous transmission of information to our senses. This continuous stream is what defines analog data. Digital information, on the other hand, estimates analog data using only ones and zeros.
For example, a turntable (or record player) is an analog device, while a CD player is digital. This is because a turntable reads bumps and grooves from a record as a continuous signal, while a CD player only reads a series of ones and zeros. Likewise, a VCR is an analog device, while a DVD player is digital. A VCR reads audio and video from a tape as a continuous stream of information, while a DVD player just reads ones and zeros from a disc.
Since digital devices read only ones and zeros, they can only approximate an audio or video signal. This means analog data is actually more accurate than digital data. However, digital data can can be manipulated easier and preserved better than analog data. More importantly, computers can only handle digital data, which is why most information today is stored digitally. But if you want to transfer video from old analog video tapes into your computer so you can edit them, you're not out of luck. You can use a digital to analog converter (DAC) to convert the analog information into a digital signal that can be recognized by your computer.
For more information on analog and digital technology, view the Help Center article.