Theoretically, unmetered means unlimited since they don't put a meter on how much you use. However, if you read the small print, you will find a lot of caveats. Plus a lot of reasons why they can throttle your bandwidth.
It's like web hosting with unlimited space. How can there be unlimited space when the servers you are on are physical entities and all physical entities have limited space? Same with unlimited bandwidth. You cannot have unlimited bandwidth when the server you are on is serviced with a limited bandwidth.
In a way, unmetered bandwidth is a marketing strategy. In another way, it's a calculated risk on the part of the host. The key is usually the speed you get. At a certain speed, there is only a certain maximum amount of traffic that you can get on your site, even if you are going at full-speed 24/7, which is never the case, in the first place. A 10Gb link does not mean you are getting that speed. It simply means that the link you are on has that maximum capacity. It doesn't even mean that the link is running at that maximum capacity 24/7 either.
Personally, I would steer clear of offers like that. I would much prefer my host to be upfront and tell me exactly what I get for what I pay.
