TIP TO UNDERSTAND EASILY
Look at dictionaries just like a reference dictionary. The key is like the word and the value is the meaning. so, we could have our mini English dictionary >>> myEngDict = { 0: "The first entry of a decimal number system", 1: "The second number", 4: "The square of 2" } Now you might want to add the meaning of 2 because someone might not understand what 2 used in defining 4 is. So >>> myEngDict[2] = "The this number in the decimal number system" so our new dictionary says: >>> myEngDict { 2: "The this number in the decimal number system", 0: "The first entry of a decimal number system", 1: "The second number", 4: "The square of 2" } Suppose you want to make definition of 4 simpler. to make it easier: >>> myEngDict[4] = "The fifth entry in the decimal number system" That will edit the value for key 4. Now let a user use our dictionary: they want to know the meaning of 1 >>> myEngDict[1] "The second number", What if they look for a number we don't have? They will get a KeyError to show that that we don't have that word in our dictionary. so we can now understand that keys are the "words" in our dictionary and values are the "meanings" of those words. Comments, questions welcomed.