What CWO Marc said.
Light inf are skirmishers often times armed with rifles. They would run out in front of the main lines in a loose formation in order to take advatage of cover, move quicker, and offer a less dence formation. They would then begin talking potshots at the enemy. Because of there loose formation cavalry could easly run them down and force them to retreat back into the main line.
Line inf were you basic soldier who formed the ranks of the main line. They were armed with muskets and bayonets. They would fire with their muskets until the enemy was softened up and then charge in with their bayonets. When charged with cavalry they would form squares with there bayonets facing out in all directions. These squares were great targets for inf and art though.
Guard inf, were the best trained and equipt soldeirs. They were often choosen because of their height and wore fancy unforms with gigantic hats. Usualy they had great disipline, never fleeing, and devistaing when they charged.
I think 1805 is much better date. Many important battles occured that year Ulm, Trafalgar, austerlitz, and Russia was an importan memeber of the third coalition which included England, Austria, and Sweden aswell.