The core material is copper, coated with a thin layer of a polyurethane, polyamide, or polyester etc resin - the so-called "enamel".
For ease of manufacturing inductive components like transformers and inductors, most new enameled wire has enamel that acts as a flux when burnt during soldering. This means that the electrical connections at the ends can be made without stripping off the insulation first. Older enameled copper wire is normally not like this, and requires sandpapering or scraping to remove the insulation before soldering.
Class 2 wire has thicker insulation layer resulting in a higher breakdown voltage than class 1 wire.
The temperature class indicates the temperature of the wire where it has 20,000 hours service life. At lower temperatures the service life of the wire is longer (about a factor 2 for every 10 °C lower temperature). Common temperature classes are 120, 155 and 180 °C.