It may be different in the EU, but in the US the major difference between them are beliefs surrounding government responsibilities.

Left wing people tend to believe in a large central government who is deeply involved in caring for its citizens. This tends to result in the government becoming more involved in people's daily life, and thus people grow more dependent on the government providing solutions to problems. More simply, the needs of the many outweigh the needs of the individual.

Right wing people tend to believe in a small central government who only intervenes when necessary. This tends to result in people being personally responsible for their own decisions and actions in life, and the consequences that come as a result. More simply, leave me alone and stay out of my business.