Encryption in transit, typically TLS, protects data moving between browsers, apps, and servers from interception. Encryption at rest protects stored data, so a stolen laptop, disk, or backup is unreadable without the keys. Modern devices and cloud services support both, but they must be turned on and configured correctly.
Key management is the hard part. Whoever controls the keys controls the data, so keys should be protected, rotated, and separated from the data they protect. Encryption is required or expected by many regulations, including the FTC Safeguards Rule for customer information.