Generally we will use metric units. Distances given in meters or centimeters (hundredths of a meter), masses in kilograms (one thousand grams), and time in seconds. Energy is then in units of joules. The unit of power is the watt, which is energy being expended at the rate of one joule per second. Frequencies are in units of Hz (named after Hertz who discovered radio waves) and corresponds to one cycle per second. These units can be modified by a set of standard prefixes: kHz is a kiloHertz or one thousand (1000) Hertz. MHz is a megaHertz or a million Hertz (one million cycles per second). Note that a megagram is one thousand kilograms and is a metric ton. A GHz is a gigaHertz which is a billion 1,000,000,000 cycles per second. There are other prefixes for decimal fractions and for even larger numbers.
Scientific notation will be used regularly in the course and text to handle very large and small numbers. They are treated according to the power of 10 that is closest or most appropriate. A power is a factor. For example 3,000,000,000 equals 3 x 10^9. The power of 10 (i.e. the exponent which is the raised number to the upper right of the 10) gives on the number of zeros following the non-zero digit for numbers greater than 1 and for numbers less than 1 the exponent is negative and is the number of zeros following the decimal point before the first non-zero number.