Django filter() lookup type documentation

I looked on Django's documentation and Googled every varation of the phrase but I cannot find any documentation that exactly describes the behaviour of lookuptypes. ``` app.objects.filter(column__lookuptype=criteria) ``` I have found documentation on which lookuptypes I can use but not what they do or how to use them. For example, I have no bloody clue what `__gte` does, but I cannot find good documentation on what it does either. Is there documentation that I overlooked? Any pointers in the right direction would be greatly appreciated. Thanks!