Here's the definition of Hallyu, lifted off a publication of the same name by Korea Tourism Organization:
Hallyu, or Korean Wave, is the growing aspiration to know more about Korean culture. The road to Hallyu is trodden everyday by new visitors who are warmly welcomed by Korean people and fascinated by the culture.
The drive to know more about Korea stimulates Hallyu to develop into more sophisticated cultural forms, which in turn, brings Hallyu to a higher level.
Hallyu goes beyond the love for television and movie stars. It is about fully appreciating the Korean culture portrayed through them.