Birds are a part of the Class Aves, which in turn is part of the Phylum Chordata and the Subphylum Vertebrata.
For more on the how and why of bird classification, see Bird Taxonomy.
The Class Aves is currently divided up into 23 orders, 142 families, 2,057 genera and 9,702 species of birds (as of 2006).
In the two tables linked to below, I have listed all the orders and families of birds. For each family the table tells you the common name of the birds in the family, the number of genera, number of species and a rough indication of their geographical distribution.
Because over half the species of birds in the world are in the one order, Passeriformes (known as the Passerines), I have put them in a second table. All the rest of the orders (the Non-Passerines) are therefore in table one.
Like most classification systems, the classification of birds was until recently based on morphological characters.
Over the last decade however much work has been done using DNA hybridisation, which give scientists a much more accurate way of viewing the affinities between bird families.
The tables here show the Orders of Birds listed in evolutionary order and are pretty much based on the publications of Sibley and Monroe (1990, 1992).