Speakers

Active speakers include an amplifier in the unit. This has the advantage of simplifying the number of cables and the system set up. However it is less flexible than a passive system and if the amplifier stops working... so does your speaker.

Passive speakers do not have an amplifier in the unit. This has the advantage of adding flexibility to your system as well as a degree of redundancy (if an amplifier stops working you can still use the speakers). However, there are more units to carry around and they are more complex to set up.