Set of Interrelated / interacting activities that help transform Needs or Problems into Products & Solutions is a Process.
A process that is capable of Meeting or exceeding desired outcome is considered as effective. A process that consumes less resources than anticipated to meet the desired outcome is considered efficient.

If there is a Gap in the desired outcome vs actual results, the Effectiveness reduces. Similarly, if the consumed resources exceeds plans the efficiency decreases. below is a visual representation of this relationships to help understand better.

While the core intent is to be able to get to the intersection of planned vs. desired. There has to a be a conscious focus to improve the processes to have a positive impact on both efficiency & Effectiveness.