An armistice is a situation in a war where the warring parties agree to stop fighting. It is not necessarily the end of a war, but may be just a cessation of hostilities while an attempt is made to negotiate a lasting peace. It is derived from the Latin arma, meaning weapons and statium, meaning a stopping.
A truce or ceasefire usually refers to a temporary cessation of hostilities for an agreed limited time or within a limited area. A truce may be needed in order to negotiate an armistice. An armistice is a modus vivendi and is not the same as a peace treaty, which may take months or even years to agree on. The 1953 Korean War armistice  was a major example of an armistice which was not followed by a peace treaty.
The United Nations Security Council often imposes or tries to impose cease-fire resolutions on parties in modern conflicts. Armistices are always negotiated between the parties themselves and are thus generally seen as more binding than non-mandatory UN cease-fire resolutions in modern international law.
The key aspect in an armistice is the fact that "all fighting ends with no one surrendering". This is in contrast to an unconditional surrender, which is a surrender without conditions, except for those provided by international law.