Durable competitive advantage
A moat is a durable, defensible competitive advantage that protects a business from rivals over time. Common SaaS moats include: network effects, high switching costs, proprietary data, and brand. Warren Buffett popularized the term in investing.
Salesforce's moat is switching cost — once a company has 5 years of CRM data, custom workflows, and 200 integrations built on Salesforce, leaving is extraordinarily painful.