The AGP is shortened for Accelerated Graphics Port or Advanced Graphics Port and it represents a high-speed point-to-point channel for attaching a video card to a computer's motherboard.

Since the development of graphics card where very progressive PCI slot, a bus with shared bandwidth, was inadequate to handle new and fast graphics accelerators. This led to the development slot dedicated to graphics adapters. The first appearence of AGP slot was on system boards based on Socket 7 Pentium and Slot 1 Pentium II processors.

Available versions of AGP:

AGP 1x - A 32-bit channel operating at 66 MHz, a maximum data rate of 266 megabytes per second (MB/s), 3.3 V signaling.
AGP 2x - A 32-bit channel operating at 66 MHz, a maximum data rate of 533 MB/s, 3.3 V signaling.
AGP 4x - A 32-bit channel operating at 66 MHz, a maximum data rate of 1066 MB/s (1 GB/s), 1.5 V signaling.
AGP 8x - A 32-bit channel operating at 66 MHz, a maximum data rate of 2133 MB/s (2 GB/s), 0.8 V signaling.

Nowdays AGP is considered to be absolete in favor of PCI Express.