title: What is the purpose of the light blue rectangle positioned in same column as the breakpoints in the Visual Studio interface?
body: <p>I accidentally pressed some keys in Visual Studio 2010 and ended up with an icon I never saw before placed where the breakpoints are usually placed:</p>
  
  <p><img src="https://i.imgur.com/aZTmw.png" alt=""></p>
  
  <p>Anyone can tell me what it does and how can I remove it?</p>