A concord is an agreement. If you want to watch a romantic comedy and your date wants to watch a horror film, you might compromise and come to a concord by agreeing to watch an action comedy.
Concord can be used as a verb meaning "to arrange by agreement," but this usage is rare. Much more common is concord used as a noun. The United Nations could work tirelessly to establish a concord between warring nations, or you might even work to establish a concord among the warring factions on your cheerleading team. A concord brings peace and harmony — just like a peace treaty.