Analogue is a physical form of transmitting sound, its bandwidth is unlimited and uses vibrations to send sound, where as digital has a restricted amount of bandwidth available. There are many different opinions when it comes to which format is better to display sound and both analogue & digital have there strong suits e.g. digital has a longer expiration date than analogue, but analogue sounds warmer to humans which is why many thinks its better.
The different types of analogue signals we looked at where vinyl records made with aluminium & magnetic tapes, but there are many other ways in which to transmit an analogue signal e.g. Televisions & ultrasonic devices.