Can a contract become null and void due to one party not understanding what exactly it was that they have was signed?

This would be very hard to prove. Ignorance may be bliss but it is no excuse. If there had been a question about the contract they should have asked questions prior to signing it. If there was an attempt to cheat the person who signed it by confusing the issues or misleading them, then that is illegal but you must be able to prove it.