Which type of certificate is generated by a user for their own purposes?

A self-signed certificate is generated by an individual or an entity for their own use, without the need for a trusted third-party certificate authority (CA). This type of certificate is particularly useful for testing, development, or internal services where public trust is not necessary. Because the signer and the issuer of the certificate are the same, a self-signed certificate does not carry the same level of trust as a CA-signed certificate, which is validated by an external authority.

In practice, self-signed certificates are often used in situations where security is still important, but the cost and complexity of obtaining a certificate from a CA is not justified. It's common for developers to use self-signed certificates during the development process, or for organizations to use them internally when setting up secure communication channels where external verification is not required.

Other certificate types, such as public, CA-signed, and third-party certificates, involve a level of trust established through verification by recognized certificate authorities, which do not apply to self-signed certificates.