Silver certificates were an older form of paper money circulating in the US from the late 1870s until about the 1960s. Still legal tender, silver certificates are sometimes seen in modern circulation but they will usually be grabbed up by collectors. Since 1964, they can no longer be exchanged for silver.
Silver certificates look like normal "old" money. Silver certificates, as well as gold certificates, were used at a time when paper currency was putatively backed up by governmental silver and gold reserves. Although interesting and collectible, worn or damaged silver certificates do not command a significant premium over their face value.