With PKI you're trusting a certificate chain up to a CA you already trust, by way of your OS or browser vendor.
A domain can layer on HSTS to that, which directs clients to additionally refuse to trust a new cert for a domain until the one you currently trust has expired.
A domain can layer on HSTS to that, which directs clients to additionally refuse to trust a new cert for a domain until the one you currently trust has expired.