This summary is not the rule. The rule text controls.
Lawyers must be honest in all their ads and communications about their services. This means they cannot lie, but they also cannot tell a half-truth that leaves out important details. If leaving something out would cause a reasonable person to get the wrong idea, that counts as misleading even if nothing said was technically false.
One common example is when a lawyer advertises past wins. Saying "I won a $1 million case" might be true, but it could give people false hope that they will get the same result. Every case is different, and ads that suggest otherwise can be considered misleading. Adding a disclaimer that past results do not guarantee future outcomes can help avoid this problem.
Lawyers also cannot make vague claims that their services or fees are better than other lawyers without having real facts to back that up. If a claim sounds specific enough that a reader would believe it was proven, the lawyer needs to actually be able to prove it.