Why do we need salt and RFC in generating AES encrypted message

I'm not very familiar with encryption and new to this, I'm just learning it right now by code review of one of the class we have in an application to encrypt a password using AES. Would anyone explain to me why do we need to have salt and RFC.

Example Snippets: passing parameters compose of input, salt and rfc string.

public static string AesEncrypt(string input, string salt, string rfcpassword)
{
  //code here...
}