scientific notation
Scientific notation is a compact way to write very large or very small numbers using powers of ten, so you do not drown in zeros. The speed of light is 300,000,000 m/s; the mass of an electron is 0.000000000000000000000000000000911 kg. Written out, these are unreadable and easy to miscount. Scientific notation tidies them up.
A number is written as a coefficient between 1 and 10 times a power of ten: a times 10^n. The exponent n counts how many places the decimal point moves, positive for large numbers and negative for small. So 300,000,000 becomes 3 times 10^8, and 0.00045 becomes 4.5 times 10^-4. To multiply such numbers you multiply the coefficients and add the exponents: (3 times 10^8) times (2 times 10^-2) = 6 times 10^6. It also makes significant figures explicit, since every digit in the coefficient is significant.
Beyond tidiness, this notation is how you handle the enormous range of scales in physics, from galaxies (10^21 m) to quarks (10^-18 m), on the same page. It pairs naturally with order-of-magnitude thinking, where the exponent alone tells you the ballpark.
The Earth-Sun distance is about 150,000,000,000 m. In scientific notation that is 1.5 times 10^11 m, three digits instead of twelve, with the '11' telling you instantly it is a hundred-billion-metre scale.
Powers of ten tame the very big and the very small.
On calculators and in code, 1.5 times 10^11 is often written 1.5E11 or 1.5e11; the 'E' means 'times ten to the', not the number e (2.718...).