A Laser Proof is a type of proof print used in the printing industry. Basically, it is a printout of either an element of a page (such as an advertisement), a full page, or a full publication.
Laser proofs are - as the name implies - done on an industrial-grade colour laser printer, and are a rather accurate representation of the final printout. However, it is not completely accurate: When printing high-volume print runs, Print Plates and ink are used, and the raster and colour process (see CMYK, CcMmYK, Pantone and Colour Processes) will make some difference from the laser proofs.
Furthermore, laser proofs cannot accurately emulate the use of specialty inks, such as metallic inks, shimmering inks, or inks that have special colour pigments in them (you are probably familiar with inks that look either red or green, depending on what angle they are seen from).
If specialty inks are used, or if it is especially important that the proofs are completely accurate, wet proofs are used - at a much greater expense.