question about winrar passwords

[Hero]

hi amitophia
I'm not a professional in encryption algorithms,but I know that AES is an symmetric
algothirm,that means the encryption and decryption keys are the same.
What do you mean by:

You can speed up WinRAR breaking by brute-forcing decryption key, not password.

You mean that password is deferent by the AES encryption/decryption keys?
(I always think that they should get the AES 128bits key by making a simple
padding from your password.)

sincerely yours