An intermediate certificate has a similar purpose to the root certificate – its only use is to sign other certificates.
However, an intermediate certificate is not self-signed.
A root certificate or another intermediate certificate needs to sign it.
en.wikipedia.org/wiki/Public_key_certificate#Self-signed_and_root_certificates
In the X.509 system, there are 2 types of certificates:
A CA certificate can issue other certificates.
The top level, self-signed CA certificate is sometimes called the Root CA certificate.
Other CA certificates are called intermediate CA or subordinate CA certificates.