How this dictionary gets the data?

Can anyone explain me this ? This function takes a string and counts the frequency of each word and returns a dictionary with word,frequency. I dont understand how the dictionary gets data.

def count_words(text):

text = text.split()
words = {}
for i in text:
    if i in words:
        words[i] += 1
    else:
        words[i] = 1
return words