The fourth criterion stresses the importance of choosing goals that matter. A bank manager's goal to "Make 50 peanut butter and jelly sandwiches by 3pm" may be specific, measurable, attainable and time-bound but lacks relevance. Many times you will need support to accomplish a goal: resources, a champion voice, someone to knock down obstacles. Goals that are relevant to your boss, your team, your organization will receive that needed support.
Relevant goals (when met) drive the team, department and organization forward. A goal that supports or is in alignment with other goals would be considered a relevant goal.