What is a distribution
What is a distribution (distro)
Linux is different - but don't worry
There is a whole new language - but you can learn it a little at a time as you go along. This page sets out to explain some of the things that are fundamentally different, so that you are immediately more comfortable.
So what is a distro?
There is no equivalent in the Windows world. The basis of any distribution is the linux kernel, which is frequently updated, but is the same for everyone. On top of that there are other layers which can affect how your desktop looks. Most people do not want to have to make all those decisions - and it takes a lot of technical skill to set up a desktop doing it all yourself- so distributions are made. Think of it in terms of brand names. You may have Mageia, Fedora, Debian, Kubuntu or one of many others. All will offer you the same applications - you will be able to follow tutorials in any of them - but they will have their own look and feel, and sometimes there are minor differences.
When you find a difference and don't know what to do
If you find that the instructions don't work for you, visit the forum and ask. Someone will help you with the differences.
If you feel more comfortable asking questions by chatting, How to chat with other KDE users will help you set up and get chatting 
What distributions are there?
There are too many distros to be listed here, and new ones keeps popping up. If you want a comprehensive overview of Linux distributions, try DistroWatch.
The number of distributions is overwhelming, but don't worry. Unless you have very specific needs, most distros should be fine. Things to look out for are:
- Does the distro support my hardware?
- Has it been updated recently - say, within the last year or so?
- Is the software I want easily available (i.e. in the repositories so you don't have to compile it yourself) and well integrated in the system.
- Does it support my native language?
It can be difficult to find all the information you need from the distro homepages. Fortunately, many distros support Live CDs allowing you to test before installing.
How to make installation media
The most common method to get a distribution is to download it from the distributions homepage. Beware, that distributions are large - typically 500 MB to 4 GB, so you need a fast web connection. Alternatively, some distributions offer to ship an installation CD or DVD for a small charge. Also some Linux magazines come with a DVD, and often carry a full distro. Perhaps the easiest solution is to ask a friend - if you know any Linux users. Most distros are open source, so it is perfectly legal to copy and redistribute them.
If you downloaded the distro, what you have is one large iso file. Now you have to burn a CD, DVD or USB drive. It is important that you don't burn it like any ordinary CD/DVD. Your burning software should have a special option for burning images (or iso files).