This summary is not the rule. The rule text controls.
Lawyers can't agree to limit their own right to practice law in exchange for something else, and they can't ask other lawyers to do this either. This comes up in two main situations.
First, when a lawyer joins or leaves a law firm, the firm can't make them sign an agreement saying they won't compete for clients or practice in a certain area afterward. This protects a lawyer's ability to keep working in their field even after they leave a job. The one exception is retirement benefits. A firm can set up a retirement plan that pays out only if the lawyer actually retires from practice.
Second, lawyers can't use these restrictions to settle a lawsuit. For example, if a lawyer is representing someone suing a company, the company's lawyer can't offer to settle the case on the condition that the plaintiff's lawyer agrees never to take on similar cases against that company again. This kind of deal might benefit the two sides in that one case, but it hurts other people who might need that lawyer's help later.
If a lawyer breaks this rule, the punishment is a public reprimand. This is a formal, on the record statement that the lawyer did something wrong, but it does not take away their license to practice law.