A key term when discussing encryption these days is end-to-end (E2E) encryption. The idea with E2E encryption is that data is kept confidential between the encryptor and the intended receiver. This might seem an obvious requirement, but not all so-called secure systems offer this level of protection.
Take for example SMS messages on your phone. The communication between your mobile phone and the local radio mast is indeed encrypted, but from that point on—until the message reaches the radio mast close to the receiver’s mobile phone—the SMS message is sent in the clear. The mobile phone company could, in theory, read your messages.