Brit Pop was a British movement from early 1990s onwards (a term coined by the press and much debated which release spearheaded it; with Suede's debut album or Blur's Popscene single). It grew out of the indie and Madchester scenes of the previous decade and was heavily influenced by the British rock bands of the 1960s, in particular The Beatles, The Kinks and The Small Faces. It was seen as a backlash against American styles, most particularly Grunge. Heavily melodic, with a traditional bass / guitar / drums /keyboard lineuup, Oasis and Blur took the style around the world with much success. It was, as a style, essentially finished by 2000.
Brit Pop should not be applied to bands / acts from the sixties or outside this defined era. Just because a band is British, or British and recorded in this era, that does not make them Brit Pop. Use carefully.