In the previous videos, you've learned what data-based advertising is and where the data used to optimize ads comes from. By the end of this video, you'll have a better understanding of what data actually is and what types of data records exist. So, Lets get started. As you most likely know, every website is made of code and that code is stored on the publishers web server. Every time someone interacts with the website, they tell the server which pieces of the code to display. In every request they made for pieces of code or elements of the website, leaves a record in the server. That record is referred to as the web server log and it looks like this. Basically, it looks like a string of code. This code may look foreign to us, but it's not too difficult to understand its components. First, you see a series of numbers and that's the person's IP address. It tells the server where to send the data. Next is a unique identifier. This is how the server recognizes who is asking for the information and this identifier is typically pulled from the person's browser, and it's usually a sequence of characters. Note, that this is not personally identifiable information, so no names or physical addresses are stored here. Next, if the website requires the person to login, there may be a username here. Next, there's a date and a timestamp of when the information was requested from the server. After that, it's a string of code that identifies, what information the person is requesting and this is how the server finds the right piece of data to return. The string of code is embedded in the links on the website, so that you can click on a link and give an instruction to the server at the same time. Next, you will see a number that tells us whether the information was successfully provided to the person, 200 means successfully delivered, while 404 means error. Finally, another number reflects the size of the content file, that the person has received. While every interaction leaves a trace in the publisher and advertisers servers. The servers, often also send some information back to the person and store it in their browser as a cookie. A cookie, is a formative piece of text stored in a person's browser. Cookies, contain information on when the person accessed the website, saw an ad and when they clicked. Sometimes, login information is stored as well. Cookies, allow a server to connect multiple interactions from the same person and this diagram shows how they work. The person requests a page through the browser, to the server it looks like a browser requesting a page. When the server gets this request, it sends the page the person asked for back. But alongside the page, it also sends a tiny text file that is placed inside the person's browser. The next time the person requests the page from the same server, the requests will come with a cookie attached. Now, the server has a little bit of information about the browser that's asking for the page. While cookies can be a great way to connect the person's interaction with the server and pass them information back and forth. They do have some challenges. Ideally, the cookie would function as the memory of the interaction between a website and a person and with that memory intact, navigation would be smoother for the person. The website would know what actions they took, it might remember settings they like, or pages and ads they saw. But people don't use just one browser for all their interactions with the website. They may use different computers, different browsers and mobile devices. Cookies, don't work across devices and the memory trace is lost. People, can also erase cookies from their browser, which erases the memory for the publisher and the advertiser. One of the major complications with cookies, is that they don't work on mobile apps. As a result, it's hard for a publisher to link behavior from a person on its website, to behavior on its app. For websites where people login, a user identifier, a UID can be created. A UID, is a unique number assigned to someone's account, that can be associated with all their logged in behavior. All interactions regardless of browser or device, can be connected to a UID. With a UID, interests, behavior and demographics can be stored. Anytime a person logs in, further behavior can be associated with them. It is important to note that UIDs use a number or text files, but they don't store personally identifiable information. It's also common practice in the digital world to hash the information. This means that the original data item gets translated into a hash data item by applying an algorithm. As a result, what is stored is unrecognizable unless you have the hashing key, another algorithm that lets you revert the information back to its original form. This is an extra safety measure to help keep people's privacy intact. This video might have been a bit technical, but you now should have a good understanding for what types of data records are collected to customize user experience online. In the next video, we'll find out who owns, collects and stores user data. See you there.
