A severability clause (also called a “savings clause”) is found in many contracts. The point of including this clause is to make sure that the rest of the contract is enforced even if one or more provisions are found to be unenforceable.
This is accomplished by “severing” the unenforceable term(s) from the contract while preserving the remaining terms.
You can imagine the disaster that might ensue if a complex contract was voided in its entirety merely because one term of little consequence was found to be unenforceable. In those circumstances, it could provide a strong incentive for a party who no longer wanted to be in the contract to challenge a provision—no matter how minor—in an attempt to void the entire agreement, thereby discharging that parties’ obligations.