Mathematics/Exponential Notation
See also: MathML
Exponential notation is one way to describe large numbers. In handwritten and academic mathematical notation, exponents are noted by raising the exponent above the base number ("superscript"). Originally this could not easily be displayed on computers, so hackers and programmers took to using the caret symbol (^) to mark the seperator between the base number and exponent. In this Wiki the caret usage is maintained, due to limitations of the Wiki software.
In science, exponential numbers are often notated by using the letter "e". An "e" is equal to "times ten to the power of X", so 3.5e7 means "three point five times ten to the power of seven", 3.5 * 10^7, or 35000000.
Living within the limitations of simple text on the internet can be extremely frustrating for mathematicians and scientists. For this reason, the markup language MathML was created  it can correctly display mathematical symbols in a crossplatform manner using XML.
Example
Googol is 10^100, which is a very large number indeed. This is why the search engine Google is named thus.
Reference table
Word, Notation, Prefix, Numeral
10^0
One

1
10^3
Thousand
kilo
1,000
10^6
Million
mega
1,000,000
10^9
Billion
giga
1,000,000,000
10^12
Trillion
tera
1,000,000,000,000
10^15
Quadtrillion
peta
1,000,000,000,000,000
10^18
Quintillion
exa
1,000,000,000,000,000,000
10^21
Sextillion
centi
1,000,000,000,000,000,000,000
10^24
Septillion
deci
1,000,000,000,000,000,000,000,000
...Octillion, Nonillion, Decillion...