What is a Load?
The reason why we want to build circuits is to make electricity do useful things for us. The way we do that is by putting things in the circuit that use the current flow to light up, make noise, run programs, etc.
These things are called loads, because they “load down” the power supply, just like you’re “loaded down” when you’re carrying something. The same way you could be loaded down with too much weight, it’s possible to load down a power supply too much, which will slow down the current flow. But it’s also possible to load down a circuit too little - this may let too much current flow, which can burn out your parts or even the power supply.