rfc 1918. ip addresses fall into classes, of those a few ranges are reserved for "private" non routable.
You may recognize them, they mean they are local addresses and by extension only have relevance on a local network. they are not Internet addresses and thus they need not be unique. Millions of business's and homes all across the world use these addresses for the addressing then they "nat" or network address translate into a real address.
Likely the linksys or 2wire router at your house does this, takes the local network - which may be 1,2 or 200 devices and translates them into a single address. natting reduces the amount of ip addresses needed because not every "device" on the internet needs an ip. Your iphone or blackberry is also on a large 10.x.x.x network, and accesses the internet via logical gateways. same concept.
as for running out of ipv4 space, yawn. been said for over a decade. it will happen tho, but it wont be due to us, nor is there much we can do about it. the growth in india and china will consume it. Luckily the ipv6 path is well founded, with good support in routers and operating systems for nearly a decade. as those countries come upon the limitations -- they -- not us -- will be forced to go the ipv6 route to continue growth.