The law is too complex, and there are too many different fields of law for all lawyers to be able to handle all problems.
Some lawyers specialize in narrow areas, like antitrust law or banking law.
Others specialize in criminal or personal injury law. On the other hand, some lawyers are general practitioners and can handle a variety of legal problems that individuals are likely to encounter. In the unlikely event that you don't know the legal category into which your problem falls, you can describe it to a lawyer, and he or she can help you figure it out. Some law firms are staffed with a variety of specialists. So while one lawyer may not be able to handle your problem, someone else at the firm possibly can.