A colleague created a map for me using ArcGIS for Desktop and emailed it to me in another state. I was able to open the document using ArcGIS for Desktop but no map appears, why?
She also sent it to her boss using data from a central fileserver and again the map didn't appear why?
I would guess that she only sent the .mxd file (which is the Map Document). You need the files the the map document references (rasters, vectors, databases, etc) in order to view them as they aren't stored in the .mxd file.
You should also read this article about Shapefile file extensions.
Assuming you are using shapefiles, you need, at a minimum:
for each shapefile. It will generally come with more file extensions, such as .prj .sbn .xml
