Historic cache of goods and/or information
A method of communication with people in the future. Sometimes created and buried with much hoopla during some celebration such as a World Fair, cornerstone laying for a building or other event. Many times embedded in the cornerstone of a building as it is built - city hall, major sports arena, etc.
A time capsule is sometimes buried by an individual in a special place which will be dug up by a descendant.
Contents can include such things as newspapers, recordings, memorabilia
Three time capsules are "buried" in space. The Voyager Golden Record has been attached to two spacecraft for the benefit of spacefarers in the distant future. The Keo sattelite will be launched in 2006, carrying individual messages from earth's inhabitants addressed to earthlings in the year 52,006, when Keo will return to Earth.