Shapefile

The shapefile, or ESRI Shapefile, is an old and popular file format that's supported by most desktop GIS systems, but is rarely used directly in web maps. Shapefiles can be a moderately efficient way to transfer larger amounts of spatial data, but they have quirks and limitations that you should be wary of:

• A shapefile is not one file, but a collection of files - typically .shp, .dbf, and .prj, but there are more than 10 different files that are often also included in the group.
• The data attached to a shapefile, contained in the .dbf file, limits the length of attribute names and values to 255 characters.
• A given shapefile can only contain one kind of feature, whether point, polygon, or linestring.

Placemark supports shapefiles as a .zip file containing .shp, .dbf, and .prj, or as those files dropped or selected into the map in one operation.

References

• Shapefile on Wikipedia