Explained by @mani1 as:
If you have two or more amplifiers in your car, you need to route power wires of all those amplifiers to the battery which creates clutter and is expensive as you need large lengths of power wire (from amplifier till battery for each amplifier). With a distribution block installed in the trunk, you only need short strands of power wire for each amplifier which go into the input end of distribution block and only a single wire through output end goes to the battery.
For more queries, please google or make a thread in the relevant Car Audio section and Ill be happy to help
A diagram to help understand
