A level Physics Help

Yes your explanation is correct up to that point. The conduction band is the range of energy levels that electrons can occupy above the valence band. Electrons in the conduction band are free to move and can carry an electric current. When an electron in the valence band absorbs enough energy it can jump to the conduction band leaving behind a hole in the valence band. The energy required for this transition is called the band gap. In conductors the valence and conduction bands overlap allowing electrons to move freely between them. In semiconductors the band gap is small enough that electrons can be excited into the conduction band by thermal energy or light. In insulators the band gap is large making it difficult for electrons to jump from the valence to the conduction band.