需要解释Caesar密码中的代码

def caesar_encrypt(plain_text, shift):
    encrypted_text = ""
    for char in plain_text:
        if char.isalpha():
            if char.isupper():
                encrypted_char = chr((ord(char) - 65 + shift) % 26 + 65)
            else:
                encrypted_char = chr((ord(char) - 97 + shift) % 26 + 97)
        else:
            encrypted_char = char
        encrypted_text += encrypted_char
    return encrypted_text

def caesar_decrypt(cipher_text, shift):
    decrypted_text = ""
    for char in cipher_text:
        if char.isalpha():
            if char.isupper():
                decrypted_char = chr((ord(char) - 65 - shift) % 26 + 65)
            else:
                decrypted_char = chr((ord(char) - 97 - shift) % 26 + 97)
        else:
            decrypted_char = char
        decrypted_text += decrypted_char
    return decrypted_text

plain_text = "Hello, World!"
shift = 3

cipher_text = caesar_encrypt(plain_text, shift)
print("Cipher text:", cipher_text)

decrypted_text = caesar_decrypt(cipher_text, shift)
print("Decrypted text:", decrypted_text)