Ansys is a suite of finite element based applications that provide real-world simulations of structural, thermal, electromagnetic and fluid-flow behavior of 3-D product. All Ansys products integrate with CAD environments. This is normally access via the WorkBench interface.
Fluent is a Computational Fluid Dynamics (CFD) software package commonly used in engineering education for research in fluid mechanics. ANSYS purchased Fluent recently and has incorporated Fluent functionality into Ansys on an ongoing basis. The Ansys WorkBench product is how you access this functionality. Note Fluent 2d and 3d and Icepak products are available outside of WorkBench.