Final answer:
Key Performance Indicators (KPIs) are the best-defined measurements for tracking an organization's progress towards its objectives. They are quantifiable and play a critical role in linking social media engagements with actual business outcomes like sales.
Step-by-step explanation:
The measurements that define and measure the progress of an organization toward achieving its objectives are best defined as Key Performance Indicators (KPIs). These are quantifiable measures that organizations use to gauge or compare performance in terms of meeting their strategic and operational goals. KPIs are not only about tracking followers, likes, or comments on social media platforms but are also critical in understanding how such engagements translate into more concrete outcomes like sales contacts and actual purchases. KPIs are measurable and motivational, helping businesses to know when they have achieved their goals.