Simple, one exists and one doesn’t…
Every day I come across web hosting companies who offer unlimited bandwidth and/or disk space and to this day I have never found one of these unlimited hosts that doesn’t have a fair usage clause in their terms of service but before we look at this situation, we really need to define these two words:
Definition of Unlimited
1. not limited; unrestricted; unconfined: unlimited trade.
2. boundless; infinite; vast: the unlimited skies.
3. without any qualification or exception; unconditional.
Definition of Unmetered
Not metered, not charged on a meter (as Internet bandwidth).
The key thing to point out here is that unlimited means with restrictions of any kind whereas unmetered is simply a value that is not measured.
Now, if a host is offering unlimited bandwidth but has a clause in their fair usage terms that says something like “we reserve the right to suspend your site if you have an impact on other users” then it is not unlimited as it is restricted. Hence it is a lie, an untruth, a porkie…
But if a host says it is unmetered bandwidth then they are saying that they don’t actually measure the bandwidth you use.
From a geek point of view, the technical difference is that all servers are connected to the outside world via a network card attached to a router. These cards are only physically capable of carrying a certain amount of bandwidth as they are limited in the speed of transfer.
For example, if you have a 100MBit card, there is a limit to the amount of bandwidth the card can carry. You can, if the connection is unmetered, max out the capacity of that card each day, every day as you have reached the limit that it can handle.
As for disk space, the only companies that can offer “true” unlimited space are the Googles and Amazons of this world. Between these megaliths, they actually own the capacity to offer this level of storage. That why when you see “bobs best hosting” offering unlimited bandwidth/storage for 2p per year you should run away, quickly…
These hosts are basically overselling their servers. Overselling is simply where they will load as many accounts onto a server in the assumption that not everyone will use the available resources. They will also boot off users who use too much under their fair usage clauses…
So in conclusion, view the word unlimited with caution. Unmetered might not sound as sexy but at least it’s the truth…