derived units
A derived unit is a unit you build by combining the base units through multiplication and division. If the base units are the alphabet, derived units are the words. Whenever a quantity is defined by a formula, its unit is derived from the units of the things in that formula.
For example, speed is distance divided by time, so its unit is metre divided by second, m/s. Area is length times length, m^2. Force is mass times acceleration, F = m a, so its unit is kg times m/s^2, which is given the shorter name newton (N). Energy is force times distance, N times m, renamed the joule (J). Many derived units get their own names (newton, joule, watt, pascal, volt) to keep formulas readable, but each is secretly just a product of base units.
This is why you should always track units through a calculation: if you compute a force and the units come out as kg times m/s^2, you know you did it right; if they come out as anything else, you made an error. Units are a free check on your algebra.
Compute kinetic energy 1/2 m v^2 for m = 2 kg and v = 3 m/s. The number is 9, and the units are kg times (m/s)^2 = kg times m^2/s^2 = joule. The units confirm you really produced an energy.
Track the units and they tell you what you computed.
A named derived unit and its base-unit form are equal, not different: 1 N and 1 kg times m/s^2 are the same thing written two ways.