Many geoprocessing tools allow you to specify a processing extent, in which only features or raster cells inside the extent rectangle will be processed. Processing extent can be used to define the geographic area of interest to be applied to a geoprocessing tool. The extent is defined as a rectangle with minimum and maximum x (longitude) and y (latitude) coordinates. You can also think about the coordinates that make this rectangle as left (minimum x), right (maximum x), top (maximum y), and bottom (minimum y).
Sometimes the extent will define the area within which to create feature or raster data; for example, when you specify a constraining extent for the Create Random Points tool, and all points will be inside the extent rectangle.
When an extent is used to process feature or raster data, the extent rectangle is used to select, but not clip or cut, the data for processing (any feature or raster cell that is inside the extent rectangle will be processed in full).
Set the extent
You can enter coordinates into the extent left, bottom, right, and top coordinate boxes.
You can also click the drop-down list above the coordinate boxes and choose to copy the extent coordinates from the current map display, a layer in your map, or a dataset path.