A leased line is a bidirectional telephone line that has been rented for private voice, data exchange or telecommunication use. Typically, large organizations purchase leased lines from telephone message carriers to interconnect different geographic locations. In some contexts, a leased line may be referred to as a dedicated line.

A leased line is a reserved circuit between two communication points that is always active and rented for a monthly fee. Leased lines are dedicated, meaning that any bandwidth associated with the leased line is solely for private, organizational use. This is different from traditional telecommunications methods that reuse the same circuit through switching.
Leased lines create a constant tunnel between two points for continuous data flow. Typically, the first location is a corporate office with the second location set as another corporate office, a data center or a corporate wide area network (WAN). The line itself runs on fiber optic cables that enable large bandwidth and high speed.

Large businesses use leased lines for a variety of uses, including:

Providing internet access.
Linking computers and servers together from multiple locations.
Making phone calls.
Enabling staff with remote access.
Carrying data and internet traffic within a network.
Streaming multimedia.

When compared to alternatives, such as ASDL, a leased line can provide the following benefits:

Bandwidth is dedicated and is not shared between other organizations or affected during peak traffic.
Lines are symmetric, meaning upload and download speeds are identical. This is ideal for remote access, sending large files, backing up data, VoIP telephony and hosting websites on premise.
Comes with a service-level agreement (SLA) that constantly monitors and troubleshoots performance.
Higher speeds.
Greater reliability and support.