KPI stands for Key Performance Indicator and is a measurable goal used to quantify the performance of the marketing strategy. Different KPIs are used for different industries as different metrics matter more than others.
Certain businesses need to emphasize cashflow while others are target AOV for new and returning customers. This is why it's so critical to perform your due diligence early on in your online journey so that you can educate yourself on which measurements are most important to your type of business and which will be most recognizable to keep an eye on for help identifying an area of trouble. KPIs can include user engagement, site visits, bounce rates, conversion rates, referral rates, etc.