Some Certification Authorities, like Comodo, do not have a Trusted Root
CA certificate present in browsers, therefore they need a “chained
root” in order for their certificates to be trusted - essentially a CA
with a Trusted Root CA certificate issues a “chained” certificate which
“inherits” the browser recognition of the Trusted Root CA. These SSL
certificates are known as “chained root” SSL certificates.


Installation of chained root certificates are more complex and some web
servers are not compatible with chained root certificates.