Compact binoculars are exactly what their name suggests: binoculars that are not very large. What this actually means is that some concessions must be made regarding some of the features
For instance, the level of brightness and the twilight factor may be somewhat lower in compact binoculars. However, the main advantage of these binoculars is that they are lightweight and easy to carry, which means that you are more likely to take them along with you. You can easily pop them into your pocket or bag and always have them readily available. After all, it is far better to have a pair of binoculars with you, even though they may have some limitations, rather than having a top-of-the-range pair of binoculars just lying on the table at home doing nothing!