A conference call is a telephone meeting. Participants dial in using a conference bridge number, which connects them to a common virtual meeting room that can be joined by people almost anywhere in the world. The meeting organizer may also call participants individually to add them to the conference line, a practice known as ad-hoc conferencing. This link can connect callers to a web conferencing services through which they may use computer audio and possibly access other types of media and collaboration tools, including screen shares, video chats and instant messaging platforms.