An OrderedDict is a dictionary subclass that remembers the order that keys were first inserted. The only difference between dict() and OrderedDict() is that:

OrderedDict preserves the order in which the keys are inserted. A regular dict doesn’t track the insertion order, and iterating it gives the values in an arbitrary order. By contrast, the order the items are inserted is remembered by OrderedDict.

In Python, a regular dictionary is an unordered collection of key-value pairs. However, in some cases, it is important to maintain the order of the elements as they are added to the dictionary. This is where OrderedDict comes in.

An OrderedDict is a subclass of the built-in dictionary object in Python. It is similar to a regular dictionary, but with one key difference: the order of the elements in the dictionary is maintained. This means that when you iterate over the items in an OrderedDict, you will always get the items in the order they were added.

Here's an example of how to create and use an OrderedDict in Python: 

from collections import OrderedDict

# create an empty OrderedDict
my_dict = OrderedDict()

# add some key-value pairs to the dictionary
my_dict['a'] = 1
my_dict['b'] = 2
my_dict['c'] = 3

# iterate over the items in the dictionary
for key, value in my_dict.items():
    print(key, value)

In the example above, the items in the dictionary are printed in the order they were added: 'a', 'b', 'c'. If this were a regular dictionary, the order of the items would not be guaranteed.

OrderedDict is particularly useful when you need to keep track of the order in which items are added to a dictionary, for example, when you need to preserve the order of columns in a CSV file or when you want to maintain the order of a list of options for a user interface.