Can anybody tell about the use of these tools and the diffrences between them?

1. Fidelity
2. Flomerics
3. MicroStripes
4. IE3D
5. IntelliCAD
6. RTS
7. Empire
8. Sonnet
9. XFDTD

I dont know about each tool you have listed but what i can tell you is that difference in software is usually based how they solve the EM equations. They can either use Finite Element Method, Finite domain time domain, Integral equations or combition of those 3 solve methods. If you go the respective website of each software,, they usually mention what their software is based on. Other factors would be how fast their algorithm is to solve the equations.