Brightness and contrast, or otherwise the contrast ratio, are two very important features to consider, in combination with the projection distance and the maximum diagonal you want to achieve, for the selection of a projector. This particular one has a brightness of 450 Lumens and a contrast ratio of 2000:1.
Contrast indicates the difference between the darkest and the brightest part of an image and is an indicator of image quality. The image projected by a projector with a low contrast ratio appears faded and flat. On the contrary, with a high contrast ratio, it looks more realistic and with greater "depth".
Brightness indicates how much light the projector can deliver on a specific surface size. The general rule suggests that brighter projectors should be preferred in rooms with plenty of light or multiple light sources, while darker ones should be preferred in dark rooms.