Which file format is used in ArcMap to store map documents?

The correct answer is that ArcMap utilizes the MXD file format to store map documents. MXD, which stands for Map Document, is specifically designed for use with ArcMap, and it contains various information regarding the layout, symbology, data sources, and display settings for the map. It allows users to save their work and return to it later, enabling a comprehensive workflow for creating and editing maps.

In contrast, a shapefile is primarily used for storing vector data in geographical information systems (GIS), while a File Geodatabase (GDB) serves as a container for various types of geographic data, including vector and raster datasets. A layer package, on the other hand, is a way to package layers together with their data in a single file for sharing and sharing them in applications like ArcGIS Online or among users. Each of these formats serves distinct purposes within the Esri software ecosystem but does not function as a map document in the same way that an MXD file does.