An agreement that is writing and signed by both parties makes it binding on both of them hence it is enforceable by the law. So an agreement to seek an interest in real estate must be put down in writing also so that it can be enforceable by the law should problem arise.
Managed is an environment where you have automatic memory management, garbage collection, type safety, ... unmanaged is everything else. So for example . NET is a managed environment and C/C++ is unmanaged.