Exactly what @akavel said – a value may be visualized in a myriad ways and the little triangle is a menu for choosing the right way. What you are witnessing here is the most general visualization – showing you a JSON representation of an object. This one is available for pretty much any object (well, any object defining a
For this particular use case, you want to choose the one named
paper: centered – it renders the JSON to SVG using paper.js under the hood.
All this happens because the visualizers are like libraries in Luna – they are extensible. You may create your own visualization, define for which datatypes it should pop up and render the data in any way you want. This way, if you have e.g. a list of pairs of real numbers, you can choose many different representations – you can just view them as a table to see the exact values, scatter them on a plane or e.g. interpret them as points on a map.