bits and bytes
A bit (b) is the simplest unit of storage and can store only 2 things (1 or 0). Since a single bit is of limited utility, we group them together into bytes.
A byte (B) is made up of 8 bits and is THE basic unit of storage in a computer. We can store 256 things in a single byte (2^8) with values from 0 - 255. As you might guess, the more bytes that we have, the more information we can store.
In the old days, a kilobyte was considered to be a lot, but today, we speak in megabytes and gigabytes and terabytes.
[note that it takes larger addresses to be able to address all of these bytes. [see powers of 2]
The chart below shows the different prefixes used to denote larger and larger collections of bytes.

Name Abbr. Size
Kilo K 2^10 = 1,024
Mega M 2^20 = 1,048,576
Giga G 2^30 = 1,073,741,824
Tera T 2^40 = 1,099,511,627,776
Peta P 2^50 = 1,125,899,906,842,624
Exa E 2^60 = 1,152,921,504,606,846,976
Zetta Z 2^70 = 1,180,591,620,717,411,303,424
Yotta Y 2^80 = 1,208,925,819,614,629,174,706,176
From www.howstuffworks.com
A kilobyte or "K" is about a thousand; "M" a million; "G" a billion; ...
A flopppy holds 1.44 Megabyes, a Zip disk holds about 100 Megabytes, a CD holds about 650 Megabyes, a typical thumbdrive holds 4+ Gig and a typical DVD holds 4.7 Gigabytes (9.4 double sided). It would take 213 regular DVDs to make a Terabyte and over 21,000 DVDs to make a Petabyte!!
So a Yottabyte, or a "Y", is huge, almost beyond comprehension. A "Y" is 1 septillion, 208 sextillion, 925 quintillion, 819 quadrillion, 614 trillion, 629 billion, 174 million, 706 thousand, one hundred and seventy-six.
So remember: if you got a "Yott", you got a LOT...