What was the difference between the Napoleonic French skirmish infantry units called tirailleurs, chasseurs, voltigeurs, and flanquers?

These names were all used variously to describe units of light infantry, but in different contexts:

The voltigeurs were one of the six (after 1808) companies of every battalion of line and light infantry, and one of the two elite companies of every battalion (the other being the grenadiers or carabiniers). While the grenadiers were veterans picked for being tall and imposing, the voltigeurs were chosen from the shorter but more agile men of the battalion to give them an organic scouting and skirmisher element, and they received the extra pay due grenadiers as well as sabres. Being elite companies, colonels were supposed to pick the men for them carefully, and units that had seen no action were not supposed to have any until they did.
Chasseurs were the "center" (i.e. non-elite) companies in light infantry regiments and battalions: each battalion would have one company of carabiniers, one of voltigeurs and four of chasseurs. They had distinctive uniforms like all light infantry and were theoretically specially trained in skirmish warfare, but they could and did operate in close order (just as line infantry could often deploy as skirmishers as needed).
Flanqueurs and tirailleurs were general descriptors of light infantry (en tirailleur meaning roughly "in skirmish order"), but with the formation of the Young Guard (which got the pick of each conscript class) units of flanqueurs and tirailleurs were added, with either -chasseurs or -grenadiers appended to the name. As soldiers of the Guard, they got a number of perks, and their officers and NCOs came from the veterans of the Old Guard, so their training and leadership would likely be of a high order, but their uniforms and equipment weren't much different from regular line and light infantry.