You can't move a muscle in this day and age without some clever clogs down the pub telling you in that casual smug way how they streamed item X to device Y and managed to enjoy something that only they were smart enough to do, most often for free, and usually while lying in bed having their toe hair waxed.
The tragedy is that they probably deserve a bit of techno-street cred and geek back-slappery. On the flipside, what everyone else shouldn't have to burden is the wondering what they're talking about at the first mention of the word "server" and then retreating back behind some silence in the hope that no one spots that you've no idea what they're talking about.
Well, don't worry. This is what we do here on What the hell is and it's why you're reading this. We'll explain the whole server thing another time but let's just deal with that streaming one today. Streaming is the sending of content - most commonly, for consumers (i.e you), audio or video content - as data from one source through some pipeline of a sort and then to a device where it's put back together again so that you can listen to/watch it. The idea is that it all happens as a real-time steady flow of information so that there's neither a need to store any of it or download it first before you can appreciate it.
One very obvious, very familiar example of this is TV. You select a channel and the data stream, beamed out over the airwaves that we pay our taxes for, can then be received and decoded by some technology in your Grundig CRT, or whatever you own, and displayed for mindless staring on your ageing tube. You don't need to wait to download the entire program first and you don't need to house the data anywhere on your TV to enjoy it either. It just comes at you and disappears as easy as that.
You can, of course, choose to record the stream if you like provided that you have a suitable device - a VCR or PVR etc - and provided that the company sending you the stream hasn't wrapped up their data in such a way as to prevent you from doing so.
The reason streaming has come to the forefront of late is because now we have not only other devices to receive streams on but new sources of the content as well. The sources are largely that massive expanse of servers known as the internet and the devices are mobile phones and computers mostly.
YouTube is a classic streaming service as is Spotify. The first uses your browser and a plug-in - Adobe Flash - to decode that data stream, the other requires its own dedicated player in the form of the Spotify desktop or mobile software. Neither lets you keep the content.
Where it all gets clever and we start entering the smugness zone is that you don't need the internet to stream things. If you have a wireless router at home, then you can often stream content between devices that have Wi-Fi built in, even if your router isn't actually connected to the rest of the world. That's going to be easiest if your gadgets are DLNA compatible but, again, we can go into that one another time. The upshot is that you can play stuff that's sitting one place somewhere different without having to use any cables to connect the two or transfer any CDs or DVDs or USB sticks from one place to the other.
The added good news is that technology has recently got round to the idea of being able to stream HD content wirelessly about you home as well which means video content fit for your TV once upgraded from the Grundig to something larger, flatter and much more expensive.
That, in a slightly larger nutshell than initially intended, is streaming. All you need to keep that content flowing is a constant wired or wireless connection.