VHDL is an acronym which stands for VHSIC Hardware Description Language. VHSIC is yet another acronym which stands for Very High Speed Integrated Circuits
VHDL can wear many hats. It is being used for documentation, verification, and synthesis of large digital designs. This is actually one of the key features of VHDL, since the same VHDL code can theoretically achieve all three of these goals, thus saving a lot of effort.
In addition to being used for each of these purposes, VHDL can be used to take three different approaches to describing hardware. These three different approaches are the structural, data flow, and behavioral methods of hardware description. Most of the time a mixture of the three methods are employed.
VHDL is a standard (VHDL-1076) developed by IEEE (Institute of Electrical and Electronics Engineers). The language has been through a few revisions, and you will come across this in the VHDL community.