What would I use a power supply for? What items do you hook up to it and why? Why not just use a power strip to plug everything into?

electrics in your home are AC. Electronic components generally require DC power.

Some battery chargers are DC supply only, intended to be run off truck and car batteries. Some are higher voltage than others - the really powerful ones often require 24 volts + to reach peak output. The smaller chargers like the b6/accucel 6 50w types work out a lot cheaper if you run them off a laptop type power supply rather than spending double the amount on one that has an AC to DC power supply built in - which have been known to fail on the cheaper charger leaving an ok charger that doesnt work because its mains adaptor is nonreplaceable. DC only chargers tend to be smaller too.

edit: I use an old laptop power supply for my accucel 6 - i already had it so my charger cost less than half what it would have done if i had bought a mains powered unit.

Okay thanks.