Why can potocols on higher layers can be left unchanged?

at the following link there is a guy explaining how ssl works. In his first sentence he is saying that protocols on higher layers can be left unchanged? What does he mean? I know the osi-layer but i think i got some knowledge-issues here.

How does SSL/TLS work?

SSL (and its successor, TLS) is a protocol that operates directly on top of TCP (although there are also implementations for datagram based protocols such as UDP). This way, protocols on higher layers (such as HTTP) can be left unchanged while still providing a secure connection. Underneath the SSL layer, HTTP is identical to HTTPS.

Thank you for your help!

Talpi