The and operator evaluates to true only if both of its operands are true and false otherwise. It can be used to combine multiple conditions to form a more complex condition that must be satisfied for an object or a set of objects to meet a certain requirement. For example, if "a" and "b" are Boolean expressions, then "a and b" will be true only if both "a" and "b" are true.

Examples:

1. Suppose we have a class called Person with two attributes: age and gender. We want to define a constraint that only allows persons who are at least 18 years old and are male to enroll in a certain program. The OCL expression for this constraint would be:

context Person

(self.age >= 18) and (self.gender = 'Male')

This constraint specifies that the age attribute of a Person object must be greater than or equal to 18, and its gender attribute must be equal to Male for the object to satisfy the constraint.

2. Consider a class called Order with two attributes price and quantity. We want to define an operation that calculates the total cost of an order, which is the product of its price and quantity. The OCL expression for this operation would be:

context Order

total_cost = self.price * self.quantity

This expression defines a new variable called total_cost that is equal to the product of the price and quantity attributes of an order object. The "And" operator is not used in this example, but it could be used in a constraint to specify that the price and quantity attributes must both be greater than zero for an order object to be valid.