meaning of -> syntax in function definition

[DrakeSoft]

Hi,

I came across the following function:

def getWords(self) -> list[str]:
     with open(self.word_list_path, "r") as f:
        word_list = [line.strip() for line in f]
      return word_list

class Ui_MainWindow(QMainWindow):
 def __init__(self, word_list_path: str):
     super().__init__()
     self.word_list_path = word_list_path
     self.speller = SpellCheckWrapper(self.getWords(), self.addToDictionary)
     self.setupUi()

class SpellCheckWrapper:
    def __init__(
        self, personal_word_list: list[str], addToDictionary: Callable[[str], None]
    ):
        # Creating temporary file
        self.file = QTemporaryFile()
        self.file.open()
        self.dictionary = DictWithPWL(
            "en_US",
          .......

I am not familiar with the notation "def getWords(self) -> list[str]:" in the function definition. What does the -> mean?
Also when I invoke the file with python3 I get an error on the line:

self.speller = SpellCheckWrapper(self.getWords(), self.addToDictionary)

TypeError: 'type' object is not subscriptable

Could someone explain or provide some context for the use of -> and the error I see?