Millions and Billions, thousandths and trillionths. Numbers and more numbers. Physics is the study of the natural (physical) world, and as such uses many measurements, or constants. From the speed of light to the charge on an electron (elementary charge), From the mass of a proton to the radius of the sun, the parade of numbers marches on. The size of universe is incomprehensibly enormous (the macroscopic) and, paradoxically, reliant on the vanishingly small (the quantum):
These numbers can be gigantic or lilliputian, and to write them out in full (where possible) is an exhausting, and in some cases futile or even impossible endeavour. Nonetheless, we must have a way of writing them in sufficient accuracy. One way of doing this is to use scientific notation, by expressing the leading digits multiplied by the a power of ten. Here is a link to good explanation of how to work with scientific notation.