Software Synthesizer
A software synthesizer, also known as a softsynth is a computer program or plug-in for digital audio generation. Computer software which can create sounds or music is not new, but advances in processing speed are allowing softsynths to accomplish the same tasks that previously required dedicated hardware. Softsynths are usually cheaper and more portable than dedicated hardware, and easier to interface with other music software such as music sequencers.
Read more about Software Synthesizer: Hardware Versus Software, Types of Softsynth, Plug-in Compatibility, Typical Software Synthesizers