Logical operators
Logical operators can build compound conditions into a formula, such as two or more conditions that must be met before you choose a particular method of calculation. With logical operators, you can describe such combinations of conditions.
Use AND, OR, or XOR with two expressions; use NOT with one expression.
True only if both items are true
True if either item is true
True if either of the expressions (but not both) is true
Changes the value from False to True or from True to False
Use ApplicationReceived="Y" AND FeePaid>0 if you want something to occur only if you have received both the application AND the fee.
Use CurrentBalance0 OR CreditApproved="Y" if you want something to occur only if no money is owed, OR credit has been approved, OR both are true.
Use FeePaid>0 XOR FreeGift="Y" if you want something to occur only if EITHER a fee has been paid or a free gift has been sent, but not both (for example, if a fee has not been paid and a free gift has been sent).
Use NOT IsEmpty(FieldName) to identify records that have a value in the FieldName field.
Related topics 
About formulas