What is setClientCertificate(clientCert, password) method in Salesforce Apex?

setClientCertificate(clientCert, password)
This method is deprecated. Use setClientCertificateName instead.
Signature
public Void setClientCertificate(String clientCert, String password)
Parameters
clientCert
Type: String
password
Type: String
Return Value
Type: Void
Usage
If the server requires a client certificate for authentication, set the client certificate PKCS12 key store and password.