An Acronym for List Processor.
The secret to reading LISP is to look at the indenting. You will go mad if you count the brackets. The secret to writing LISP is to always use an editor such as Emacs that autoindents LISP code and highlights matching brackets for you.
LISP is usually run on a VirtualMachine, although modern LISP implementations can compile to MachineCode. At the time of its conception, CPUs were so slow that requiring a VirtualMachine made LISP infeasible as an implementation language for real world applications. It was therefore attempted to build processors that could run LISP directly - so called LISP machines. Like any other attempt to date to realize a certain VirtualMachine in hardware, LISP machines too failed to achieve any significance in the market and were soon forgotten.