Hey kiddo! A microsecond is a very, very tiny bit of time. It's like a blink of an eye that is so quick you can barely even notice it.
You know how we count seconds? One Mississippi, two Mississippi, three Mississippi... well, a microsecond is a million times smaller than a second.
So if you can imagine how fast one second goes by, a microsecond goes by one million times faster than that! It's so fast that we need special equipment, like fancy watches and cameras, to even measure it.
So that's what a microsecond is, a super fast and super tiny measurement of time!