What is Multitenancy in Salesforce?

Multitenancy in Salesforce is like living in an apartment building. Imagine Salesforce as a big apartment building, and each tenant in the building is a different Salesforce customer. Each tenant shares common infrastructures like plumbing and electricity (just like how Salesforce customers share the same servers, storage, etc.), but each tenant's personal items are secure in their own apartment (like each customer's data being secured in their own org).
Multitenancy allows Salesforce to serve multiple customers (tenants) from a single application instance (the apartment building) while keeping every customer's data separate and secure. This shared architecture lets Salesforce roll out updates and new features to all customers simultaneously, ensuring everyone's on the latest and greatest version!