Here's a good explanation from "Popular Woodworking".
Lacquer thinner is the solvent and thinner for all the types of lacquer, including nitrocellulose, CAB-acrylic and catalyzed. It’s the most interesting of the solvents because it’s composed of half-a-dozen or so different individual solvents. Manufacturers vary these to control solvent strength and evaporation rate.
Solvents from five different families are used in lacquer thinners, including toluene, xylene and “high-flash” (meaning fast evaporating) naphtha from the petroleum-distillate family. The other four families are ketones, esters, glycol ethers and alcohols.
All the individual solvents from the ketone, ester and glycol-ether families dissolve lacquer on their own, but they evaporate at different rates. So manufacturers choose among them to make a thinner that evaporates in steps at the speeds they want. Alcohol doesn’t dissolve lacquer on its own, but it does when in combination with these other solvents. So one or more of the alcohols is usually added to the mix to reduce cost.
The nature of lacquer is that is can be fully dissolved and still be too thick to spray efficiently. So to further thin the lacquer without adding expensive dissolving solvents, manufacturers add up to 50 percent toluene, xylene or high-flash naphtha to, in effect, “thin” the lacquer thinner.
By varying the solvents used, manufacturers can control the strength of lacquer thinner (automotive lacquers need a higher percentage of dissolving solvent) and the speed of evaporation. For example, lacquer retarders are made to evaporate slower so the lacquer stays “open” on the surface of the wood longer in order to eliminate blushing (turning white) in humid weather and dry spray (a sandy surface) in hot weather.
The purpose of using multiple individual solvents evaporating at intervals is to control the thickening of the lacquer on a vertical surface to reduce runs. The lacquer thickens quickly after being sprayed but enough of the slower evaporating solvents remain so the finish has time to flatten out. Lacquer thinner is unique among solvents for having this characteristic.
A cheaper “clean-up” lacquer thinner is often available. It’s made with a higher percentage of “thinning” petroleum-distillate solvents and doesn’t dissolve lacquer well. You will have problems if you use this thinner for thinning lacquer."