Coming from the latin tortum, meaning 'injustice'1, a tort is a civil wrong, tried in civil courts and resolved via monetary compensation. Tort lawyers bring charges that are generally divided into three categories: negligence torts, such as automobile accidents and medical malpractice; intentional torts like defamation and false imprisonment and strict liability torts, wherein a person injured - emotionally or physically - by a malfunctioning product can sue the manufacturers. Recently, the field of 'toxic torts'2 that lets people bring suits against polluting companies has also been gaining ground.
What constitutes legal liability is often outlined at a regional (or state) level, though widely speaking, there are usually three items that must be established for a successful tort case - that the person or company being sued (known as the tortfeasor) had a legal duty to the plaintiff, that they failed in that duty and that this failure caused the plaintiff physical or emotional injury.
It is important to note that tort cases only require proof via a preponderance of evidence, the third-highest burden of proof available. This has the benefit that some serious cases which failed to gain a guilty verdict in criminal courts can be won in a tort law case afterward, such as the infamous case OJ Simpson who, though found innocent of double homicide in Superior Court was proved guilty of wrongful death in a later civil court.3
2. American Bar. Toxic Torts: An Overview. Retrieved May 2, 2014, from http://www.americanbar.org/newsletter/publications/law_trends_news_practice_area_e_newsletter_home/toxictorts.html
3. FindLaw. A Lawsuit over OJ Simpson Murder Trial Suit. Retrieved May 2, 2014, from http://blogs.findlaw.com/celebrity_justice/2010/03/a-lawsuit-over-oj-simpson-murder-trial-suit.html