A dictionary is like an address-book where you can find the address or contact details of a person by knowing only his/her name i.e. we associate keys (name) with values (details). Note that the key must be unique just like you cannot find out the correct information if you have two persons with the exact same name.
Note that you can use only immutable objects (like strings) for the keys of a dictionary but you can use either immutable or mutable objects for the values of the dictionary. This basically translates to say that you should use only simple objects for keys.
Pairs of keys and valus are specified in a dictionary by using the notation d = {key1 : value1, key2 : value2 }. Notice that they key/value pairs are separated by a colon and the pairs are separated themselves by commas and all this is enclosed in a pair of curly brackets.
Remember that key/value pairs in a dictionary are not ordered in any manner. If you want a particular order, then you will have to sort them yourself before using it.The dictionaries that you will be using are instances/objects of thedict class.