Plaintext refers to information that is presented in a readable format without any encryption or encoding. It consists of regular text characters that can be easily understood by humans and machines alike. Examples of plaintext include simple text files, emails, and documents that do not require special software to read. In contrast to ciphertext, which is encrypted and unreadable without a key, plaintext is accessible to anyone who has access to the data. This makes it important for secure communication, as sensitive information should not be stored or transmitted in plaintext to prevent unauthorized access.