Every business has a fair value, its true price. Where market price tells you the price other people are willing to pay, fair value shows the value of a stock based on an analysis of the company’s actual financials (such as cash balance, revenue, operating margin, etc).
Economic Moat is a concept popularized by Warren Buffett to describe a company's durable competitive advantage. It represents the 'moat' that protects a company from competitors and helps it sustain profitability over the long term.