MODIS is an extensive program using sensors on two satellites that each provide complete daily coverage of the earth. The data have a variety of resolutions; spectral, spatial and temporal. Because the MODIS sensor is carried on both the Terra and Aqua satellites, it is generally possible to obtain images in the morning (Terra) and the afternoon (Aqua) for any particular location. Night time data are also available in the thermal range of the spectrum. You should consider time of day when ordering a scene for a specific day.
The MODIS web site, http://modis.gsfc.nasa.gov/index.php, is a good place to begin learning about this important program. This site has links to the Atmospheres, Land and Oceans groups of MODIS. Place your cursor over the Data tab and you can directly access many of the MODIS products.