Wikipedia
OTRS, an initialism for Open-source Ticket Request System, is a free and open-source trouble ticket system software package that a company, organization, or other entity can use to assign tickets to incoming queries and track further communications about them. It is a means of managing incoming inquiries, complaints, support requests, defect reports, and other communications.
OTRS is part of the Lisog open source stack initiative.
Every ticket generated by the system has persistence or "history" showing what happened to the ticket within its life cycle. OTRS has the ability to merge multiple requests about the same incident, thus making it possible to work on an incident rather than on singular requests. OTRS is a multiuser system which means that multiple agents may work simultaneously on the tickets in OTRS, reading the incoming messages, bringing them in order, and answering them. OTRS is highly scalable, capable of handling thousands of tickets per day and a nearly unlimited number of simultaneously working agents .
OTRS has integrated functionality for creating, reworking and searching FAQ texts. The FAQ texts may be incorporated into the agents' answers on tickets.
By using a multilingual web user interface, OTRS is usable independently from the respective operating systems since it is operated from a web browser. Furthermore, this facilitates the usage of OTRS by external agents or even customers participating in, working on or contributing to tickets.
OTRS establishes a framework of functions. For example, the System for Incident Response in Operational Security (SIRIOS) of the Federal Office for Information Security, Germany, is based on OTRS.