Britpop is indie pop music that came out of the UK in the the 90s, key word here THE NINTIES. These bands had a distinct pop style with very british lyrics. The two best examples of Britpop I can think of are Pulp and Blur. If you want to know more about britpop download the song Parklife by Blur or Babies by Pulp.
Blur, Pulp, Supergrass, Oasis, The Verve, Suede, Elastica, Stereophonics.
Bands that are no where near britpop and I have no idea why morons think they are britpop:
Muse (progressive rock), The Beatles (rock), The Jam (mod rock)
Britpop bands include Oasis, Suede, (one of the best bands ever despite the fact that they never made it big in the US. Much better songs than Blur. A much better singer than Blur. Generally better than Blur in my opinion. And Blur are good.) Elastica, Blur etc.