There are four core objectives PKI fulfills.

Authentication - confirming that someone is who they claim to be.

Confidentiality - encrypting data so only the authorized recipient can read it.

Integrity - guaranteeing data has not been altered in transit.

Non-repudiation - proving the origin of data so a sender cannot deny they sent it.

Most people only think of encryption when they hear PKI.

They are missing three quarters of the picture.