A time capsule contains artifacts intended to convey the lifestyle of the culture that buried them to a future generation. These artifacts are usually a select bunch of items that will generally portray the positive aspects of the culture - you would be unlikely to see Al Capone's baseball bat in one for instance!
Time Capsules are usually buried, often in a place with instructions to open then at specific dates. The Crypt of Civilization is an extreme example of this, being intended to be opened in the year 8113, over 6000 years in the future!
Time Capsules, in the form of plaques and records, have even made it into space aboard the Pioneer and Voyager spacecraft. Given the unlikely chance that there is another intelligent spacefaring civilization in existence at the moment, the probability of them being read is tiny, and even if they do get read, what are the chance of the readers understanding them.
What would I put in one? Well, a copy of the local Indian Take Away's menu would be one thing, some duck tape as well - brilliant stuff! maybe a couple of photo's of local historic buildings (and not just the pubs), a few Zeppelin and Jeff Beck records.........