VESA BIOS Extensions (VBE) comprise a VESA standard, currently at version 3, that defines the interface that can be used by software to access compliant video boards at high resolutions and bit depths. This is opposed to the "traditional" int 10h BIOS calls, which max out at the resolution of 640×480 pixels with 16 color (4 bit) depth.
VBE is made available through the video adapter's BIOS, which installs interrupt vectors pointing at itself during system startup. Unfortunately, the older versions of VBE (those bundled with the vast majority of existing video boards) supported only a real mode interface, which couldn't be used without a significant performance penalty from within protected mode operating systems, such as Windows 95 or Linux. This meant that the VBE standard was almost never used for writing video-drivers, and each video board vendor had to invent a proprietary protocol for communicating with their own board(s). Moreover, VBE does not include tools to control display refresh rate to prevent flicker, a severe problem at high resolutions.
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