Inequalities are used whenever you hear the phrases 'more than,' 'less than,' 'at least,' 'at most.'
For example, the starting salary for a particular company may be be at least $30,000 per year, depending on the person's experience and education. This means that the salary is greater than or equal to $30,000.
Another example may describe the amount of space or mass in a confined area, such as the amount of luggage that can be taken on an airplane. This means that each individual may carry at most 75 pounds of luggage when they check it in at a service counter. This restriction is placed so that the plane is light enough to safely take off and land. The inequality, in this case, is that the mass of the luggage per individual is less than or equal to 75 pounds.