A tort is a wrongful act or an infringement of a right (other than under contract) leading to a civil legal liability. Torts can be negligent or intentional.
One example of a tort is a car crash. The other drive may not have intended to hit you but due to either inattention or failure to obey highway laws or some other reason, they may have crashed into you infringing your right to the roadway. This is a negligent tort.
Another example is if someone punches you - a battery. This is an intentional tort.