August is the eighth month of the year. It has 31 days. The next month of the year is September. In the northern hemisphere August is part of summer, and in the southern hemisphere it is part of winter.
The crust of a baked product like bread is the harder, outer layer. The term crust can be applied to the hard outer layer of many other things, for example a crust of ice on top of snow.
You feel disgust when you have a sudden, very strong dislike of something. Some smells, like rotten food, are disgusting. The person in the picture is disgusted.
Dust is very fine dirt and lint that drifts through the air and settles on surfaces in your house, making them dull and grey. Dust needs to be cleaned up regularly with a soft cloth. The picture is of some cables from the inside of a computer. They are very dusty. When there is a storm that picks up a lot of dirt in the air, it is called a dust storm.
Locusts are a kind of grasshopper that form into huge swarms. When they are swarming in such large numbers they can strip crops and gardens completely.
Lust is a very strong, even uncontrolled or uncontrollable sexual desire, or a very strong craving for something. For example, "he has a lust for power".