Lawyers can indicate to their Bar their preferred area(s) of law and thus what kind of cases they prefer to handle. These preferred areas then appear on this website, for example, if you search for a lawyer.
Some lawyers do not indicate any preferred areas and deal with all kinds of different cases. You can always ask a lawyer if they have the experience required to take on your case and/or whether they are willing to take it on.
Lawyers are free to state what their preferred areas are: this is entirely on their own responsibility, and is not binding on the Bar.