As mentioned, protein is one of the factors that affect how satiated we feel after eating. By eating a little more protein, one generally feels fuller on fewer calories and stays full a bit longer, which creates conditions for resisting cravings and making better food choices. This is interesting both for those who need to lose weight and for those who "just" want a little help in making better food choices. If you're not ravenously hungry, your body doesn't scream for highly rewarding junk food in the same way.
More energy!?
Many people experience more energy when they eat more protein. However, I wouldn't say that you get more energy from eating more protein, but rather that a little more protein often helps you make other/better overall food choices, and that leads to more energy and possibly weight loss. If you can make better food choices and stay full, the conditions for having the energy to move and exercise also increase, which also contributes to feeling more energetic. In the same way, protein itself doesn't cause weight loss, but it can be a tool to successfully maintain a negative energy balance, i.e., eating less than you need, which is a prerequisite for weight loss.
