Bits-The tiniest measure. This actually is measuring down to the 1 and the 0
Byte-A byte equals 8 bits. It is not the term you usually see.
Kilobyte - or KB If you have a file which is measured in KB it means that it is pretty small. Sometimes emails and word processing documents are this size. It is from 1-999 bytes.
Megabyte - or MB From here on you just multiply by 1000 to get the next size. Megabytes go from 1000 to 999,000 bytes. 1000 bytes is the same as 1 MB. When you see anything with ,000 you know that the numbers before that will tell you how many megabytes something is. Things like photos are often measured in Megabytes and sometimes a photo is too large (too many megabytes) to be uploaded or used by a program.
Gigabyte - or GB Multiply again by 1000 and you have gigabytes. One gigabyte is 1,000,000. Most computers and other devices that you buy now tell you how many GB of storage you are getting. Movies are measured in gigabytes.
Terabyte - or TB Multiply again by 1000 and you have terabytes. One terabyte is 1,000,000,000. I only mention this because there was a time a few years ago when a Gigabyte seemed like an impossible amount of data for a computer to use, but now we think of it as normal. Right now I suppose that mainly large businesses, especially those that provide storage space for items (part of the cloud) use Terabytes as a measurement.