The daunting subjects of online marketing and search engine optimisation have at their core two very simple principles. The first is the use of 'keywords' and the second are 'links'. Links are what I'm talking about here. They are connections, or doorways, that are used to take you to websites or content within websites. The link contains a URL, which is the address of the destination. The words Link and URL in internet speak are conjoined. I use the word URL for the main part here to refer to both, not least because this post's title wouldn't sound half as good if it were: 'Who the link are you?'URLs are important because search engines such as Google use the number of URLs pointing to your content, to rate your content in context to similar sites. The more URLs that point to your site, the higher ranked it will be when people type a keyword relevant to your site. If you type 'Chasing Innocence' to Google right now, the chances are my book will magically appear somewhere, at least once, on the first page of results. That's because there are quite a few URLs on my various sites pointing to my book, along with the keywords: chasing innocence. The interesting aspect is these URLs can exist within your single site or blog, so they not only draw people to your site but can also channel people within your site to the bits you really want them to see. In fact embedding URLs within your content is vital. URLs within a web page are doorways. A web page with no links (URLs) is like a room with no doors. Once the reader has seen all there is in the room, if there's no doors there's nowhere else for them to go. So what is a URL and how do you use them?A URL is an internet equivalent to a postal address. For example, a URL most people will be familiar with:http://www.amazon.co.ukHTTP:// - Is the language your computer will use to speak to the destination when it eventually gets there. In this case HTTP is web-browser speak.WWW - Is simply the name of the computer at the destination. It's the equivalent of speaking to someone called WWW at the destination. It does not have to be WWW, it can be almost any name within certain parameters. HTTP://KDP.AMAZON.COM means I want to speak to KDP at AMAZON.COM and I want to speak HTTP (web-browser speak) to KDP when I get there.AMAZON.CO.UK - Is the address where you can find, in this case, the computer named WWW. It's equivalent to the full postal address for a building, anywhere in the world. It can be further broken down into .COM or .CO.UK or .INFO or a number of other identifiers, but knowing the breakdown and why, is no more necessary than understanding the breakdown of a ZIP code. All you need is the ZIP code (post code).That's the detail on a basic URL. You now know how to get there, you know who to talk to and you know what language to speak. But if you're linking to content actually within the site the URL will need to contain more. For instance:http://www.amazon.co.uk/dp/B006Z0KYEQ/DP/B006Z0KYEQ - These are specific locations or layers at the destination that WWW at the address AMAZON.CO.UK will take you to. The /DP can be equated to a room in the building and /B006Z0KYEQ, can be equated to something in that room.So, we can now look at the address again:http://www.amazon.co.uk/dp/B006Z0KYEQWe now know this means I would like to talk HTTP to WWW at AMAZON.CO.UK and I would like WWW to take me to the room DP and to the item referenced: B006Z0KYEQIf you type the link into any web browser right now you will find /dp/B006Z0KYEQ points to Chasing Innocence on Amazon UK.Sometimes you will look at the link and see lots of symbols towards the end of the URL. This is simply extra information WWW might use to find extra content.So how do we use these URLs? Now we understand what a URL is, actually using them is simple. You add a URL to content on your site. You might have a line of text that reads: Check out John's book on Amazon. To create a doorway to John's book on Amazon you first highlight the text and then click the add link button within the application you're creating the web content. In Wordpress it's the chain icon. In Blogger you simply click on the Link button.As creating links is a core function of any internet content tool, each will have a link creation button. Once the relevant 'Link' button is clicked you will be presented with a dialogue that requires the following:The URL - In this case: http://www.amazon.co.uk/dp/B006Z0KYEQThe Title - Which is optional. I might enter: Chasing Innocence on Amazon. Adding this might also help search engines to additionally rank the content.Open a new Window/Tab - This is quite important. Clicking a URL will take the web browser to the destination, if you want the reader to come back to the page containing your original content, you want to open a new browser window, or they might get to the destination and find a whole bunch of new doors and forget all about where they started.Once you've entered the detail you click 'Add Link' and the link will appear in your content when you publish it.So to the final and briefest stage. How do you find out what the URLs for your content are? So that you can link to it. Simples. You go to the content you want to link to on your site, then you look to the address bar at the top of your web browser. Most browsers will list the full URL. For instance if you look at the address bar right now, you will see the URL for the page you are currently reading is:http://www.wordwatchers.net/who-the-url-are-you/If you want to link to this page you highlight ALL of the URL in the address bar and (right-click) Copy it and then Paste it to a link in your content as described above.That really is it. I hope that's a little clearer than mud. If not then be sure to fire away with questions in the comment section below.