As one of the key elements of the Space Exploration Initiative, the Moon provides a waypoint for scientific exploration and travel to Mars. The Moon’s stable ground in the vacuum of space is an ideal platform for astronomical observatories. Conditions on the Moon are similar to what human beings will face on other planets, so it is a natural test bed to prepare for a manned mission to Mars. A knowledge of the lunar environment is therefore important before undertaking any missions of construction, operations, and habitation on the lunar surface. The purpose of this paper is to review and assemble information on the lunar environment so that engineers and scientists can refer to this as they begin lunar-based engineering studies. The lunar environment is categorized into three major elements: lunar physical constants, lunar atmosphere, and lunar surface. The description of lunar size, orientation, period of rotation, and lunar month are all treated as part of lunar physical constants. Lunar atmosphere includes gas composition, pressure and density, solar flux and radiation, micrometeorite flux, and lunar dust. The geophysical and geochemical properties are provided as lunar surface characteristics. The geophysical properties include terrain characteristics, topography and surface tremors; soil and rock characteristics; mechanical, thermal, electrical, magnetic, and optical properties. The chemical composition of the regolith and rocks are described in geochemical properties.