QSFP stands for "Quad Small Form-Factor Pluggable." It is a compact and hot-pluggable transceiver module used in data communication and telecommunications applications. The "Quad" in QSFP refers to the four independent channels or lanes, each capable of transmitting data at different rates. QSFP modules are widely used for high-speed connections in data centers, networking equipment, and telecommunications infrastructure. 

Key features of QSFP modules include:

1. Form Factor: QSFP modules have a small form factor, allowing for high port density on networking devices such as switches and routers.

2. Hot-Pluggable: QSFP modules are designed to be hot-pluggable, meaning they can be inserted or removed from a compatible port without shutting down the system.

3. Multiple Data Rates: QSFP modules support various data rates, including 40 Gigabit Ethernet (40GbE), 100 Gigabit Ethernet (100GbE), and other high-speed communication standards.

4. Number of Lanes: The "Quad" in QSFP signifies that the module has four independent optical lanes, allowing for increased data transfer capacity.

5. Optical and Copper Variants: QSFP modules are available in both optical and copper variants. Optical QSFP modules use fiber optic cables for data transmission, while copper QSFP modules use copper cables.

6. Applications: QSFP modules are used for a variety of applications, including high-speed networking, data center interconnects, and storage area networking.

Common types of QSFP modules include QSFP+, which supports data rates up to 40 Gbps, and QSFP28, which supports data rates up to 100 Gbps. QSFP56 and QSFP-DD are newer versions that support even higher data rates, such as 200 Gbps and 400 Gbps.

Overall, QSFP modules play a crucial role in enabling high-speed and high-density connectivity in modern network architectures.