Nope, they are not alike... well OK, they are made by the same company, and Reaktor has sampling modules, but that's where the similarities end.
Kontakt is a single purpose app... i.e. a sampler.
Reaktor is basically a visual/modular programming environment allowing people to build their own instruments from scratch.
Reason is a very capable self contained production environment with a couple of built in samplers like NNXT and synths like Malstrom, effects units and a sequencer.
You can probably emulate the Reason environment with Reaktor, but only because Reaktor let's you build whatever you want.
Basically, if you don't want to delve too deeply into sound design and don't feel compelled to roll your own instruments and environment and such, then Reaktor is not for you!
And if you still can't figure out what the difference is among all the above... well, then get Fruty Loops
Is that simpler?