--cacert (HTTPS) Tells curl to use the specified certificate file to verify the peer. The file may contain multiple CA certificates. The certificate(s) must be in PEM format. If this option is used several times, the last one will be used.

What is Cacert used for?

cacerts is where Java stores public certificates of root CAs. Java uses cacerts to authenticate the servers. Keystore is where Java stores the private keys of the clients so that it can share it to the server when the server requests client authentication.

Is Cacert safe?

Today, the current status of CAcert.org is, that their certs are not trusted and signed by non-accepted hash algorithms.