What does the colon use in the decimal place mean? When I type into wolfram the query, exp(1) in base 100, the answer comes back "2.71:82:81...."
What does the colon (:) mean?
 A: You are asking for a number to be expressed in base $100$.  That means the first "place" after the "decimal" point is in units of $1/100$, the second "place" after the "decimal" point is in units of $(1/100)^2$, and so on.  Each "place" is populated by a whole number ("digit") from 0 to 99.  Because we do not have distinct symbols for each of those possible digits, each one of those base-100 "digits" is actually written using a pair of base-10 digits.  This makes reading the number hard, so it is helpful to use a delimiter  to keep the place values separated for readability's sake.
Strictly speaking, one could leave the delimiter out, since each "place" always is populated by a two-digit "digit", so one could simply group the "digits" in pairs.
The particular number you are looking at is
$$2 + 71(1/100) + 82(1/100)^2 + 81(1/100)^3 + \dots$$
Note that the use of a colon to separate "places" when the "places" hold two-digit numbers is standard in time-keeping, which is (at least partly) in base 60:  We write 15 minutes and 8 seconds as 15:08, and each "place" can hold any value from 0 to 59.
The irony here is that the "base 100" representation of any number is precisely the same as its "base 10" representation of the number, if you just eliminate the colons and interpret each pair of digits as two distinct place values.
