Pensionable earnings are the portion of your pay on which your pension contributions are calculated.
There is a lower band of £6,032 per year and an upper band of £46,350 per year.
£6,032 per year equates to £503 per month or £116 per week and £46,350 per year equates to £3,863 per month or £892 per week.
Your pension contributions are calculated on your earnings between these two bands, not the whole amount.
Sometimes your company may choose to make contributions on the whole amount but they will inform you if this is the case. Otherwise, it’s fair to assume that your contributions will be based on your pensionable earnings.