FL Studio is both a platform for editing external data like Audacity (or more like Ableton Live) and it has its own virtual instruments and sample libraries. (also like Ableton Live and many other packages like Apple Logic, etc.) (Source)
East West Quantum Leap is a virtual instrument and sample library suite of products (with some player/articulation capabilities), mainly marketed as symphonic sounds for soundtrack scoring. (Source)
Vienna Symphonic Library is a product in direct competition with EWQL and it is pretty much the same thing, except VSL is more focused on the symphony orchestra and its sounds exclusively. It is also marketed for soundtrack scoring with a little more emphasis on music composition and music production than EWQL. (Source)
Often, a product like FL Studio (or Audacity) is called a DAW (Digital Audio Workstation). Most products like EWQL and VSL require a "host application" like a DAW to be played, although some (maybe most, these days) come with a standalone player that one can use to play the sounds even without a DAW. Still, the intention is that one would use some kind of DAW to control playback of virtual instruments and sample libraries.
There are many competing DAWs on the market. FL Studio is popular with dance, house, dubstep, and related genres, but it can do almost anything. Another product popular with those same types of musicians is Ableton Live. For straight up audio recording, Reaper, ProTools, Logic, Sonar, and Cubase are popular. All of the ones I have just mentioned can act as host applications for EWQL and VSL, and all of them except Reaper come with their own virtual instruments and sample libraries (of varying qualities and types).
Unlike the DAWs I have listed, Audacity can only process audio, and it does not act as a host application for virtual instruments or sample libraries. (Source)