How does a threshold scheme work?

What does “a threshold scheme” mean? It’s an improved version of the escrow service, when an agreement of all the parties, who have secret information, isn’t required. To get an access to the information, it`s necessary only to have an agreement of three of five parties. You can even divide all the parties into several groups: trusted and not trusted. For example, there are three parties whom you trust and three whom you don’t trust hardly. So to get an access to the secret key, you must get the agreement of two people from the trusted group and one from the not trusted or three from the trusted group and two from the not trusted group. If one of the parties lose the key, it’s not necessary to change the key. How do you think this scheme is a convenient way to secure your coins?