The top of the list of comparative characteristics is the size of the planet, with the coloured region representing the diameter of the world, and the inner circles comparing their size to Earth and Mars. This gives a good sense of scale and also reveals how these planets aren't so far off the size of Earth.
The creators of this app have used the term ‘illumination’, however, I believe the more appropriate term would be ‘temperature’, as the narration speaks more about whether the planet is hotter or colder in relation to its relative illumination indication.
The density of a planet is a strong indication of whether astronomers are looking at rocky planets or a gas planet. Rocky planets have a much higher density measurement, and all the TRAPPIST-1 planets have densities close to Mars and Earth, inferring they are most likely terrestrial.