Different bikes, especially road bikes, are built in different sizes to accommodate various size riders. Here's the simple breakdown on bike sizing. When someone says a bike is so and so centimeters, they are referring to the length of the seat tube. The length of the seat tube is most commonly measured from the center of the top tube to the center of the bottom bracket.
In the sketch above, the seat tube measures 52.8cm that makes it a 52 or 53cm bike, depending on how you like to round. When it comes to matching up people with bike sizes the chart below from the REI website is a good starting point. For example, our pretty bike in the drawing above would serve someone who is 5'4 to 5'7 very well! You can use this chart to help you determine your size range, but it is always best to test ride a bike to ensure that it will be a good match for you.
Hope this helps!Du