There is often confusion between these terms that are used to compare and measure broadband speeds. Further complicating the issue is the matter of the higher denomination size for each – megabits and megabytes respectively – since they are both referred to as “megs”.
What these terms all refer to is amounts of information – the same system is used for the storage available on your computer or smartphone. It is based on the binary system, where a bit represents a closed or open binary switch, and a byte was conventionally the smallest number (8) of bits needed to represent an alphabetical letter or charactr.
What this basically means is that there are different units of memory represented by these terms. There are 8 bits in a byte, 8 megabits in a megabyte and so on. Bits are mainly used as terms by engineers only, and users will hear more talk of bytes in most cases.
The difference between the two can be read by the case of the “b” in the abbreviation. Bits are represented by a lowercase “b”, while bytes are represented by an uppercase “B”. So Mb stands for Megabit and MB stands for megabyte. A strange exception is kilobits, which has all lower case, both “k” and “b”. The most important thing is to be able to differentiate between megabytes and megabits for broadband purposes but if you want to learn more about the denominations you can have a look here: https://en.wikipedia.org/wiki/Template:Quantities_of_bits
What this means in practice is that the length of time it takes to download a 10 MB text file on a connection that downloads at speeds of 20Mb per second (Mbps) will be 4 seconds, since 20Mb equates to 2.5MB (as we mentioned earlier, there is one Mb or megabit in an MB or megabyte). Uppercase B = byte = the bigger of the two, lowercase b = bit = the smaller of the two; bits are bigger than bytes. An easy way to remember this is how you might explain it to a child: there are 8 “bits” (slices) in a pizza, and if you were hungry you might eat it in one “byte”.
Interestingly, the word “bit” does not come from the other word “bit”, it is a contraction of “Binary Information Digit”. Byte comes from the word “bite”, but a “y” was added to avoid confusion with the already existing term “bit” (programmers type fast, and one key pressed out of line shouldn’t cause havoc).
There are more prefixes that denote greater units of bits and bytes, such as kilo-, giga-, tera-, and peta-.