This summary is not the rule. The rule text controls.
Lawyers need to work on their clients' cases with steady effort and without unnecessary delays. Once someone hires a lawyer, that lawyer has a duty to keep moving the case forward, meet deadlines, and follow through on the work that needs to be done.
This means a lawyer can't let a case sit untouched or drag things out for no good reason. Clients are counting on their lawyer to handle matters like deadlines for filing paperwork, responding to the other side, and keeping the case on track. If a lawyer drops the ball and misses important deadlines or ignores a case for too long, that lawyer is not meeting this basic duty.
This rule exists because delays can seriously hurt a client. Cases can be lost, evidence can disappear, and people can suffer real harm if their lawyer is slow or careless. The rule pushes lawyers to treat their clients' problems with the urgency they deserve, not put them on the back burner.