These are terms relevant for National Insurance contributions.
The point at which you start paying National Insurance contributions is the ‘Primary Threshold’ (PT; set at £9,500 in 2020/21).
However, workers get the benefits of NIC (including State Pension eligibility) from the ‘Lower Earnings Limit’ (LEL; set at £6,240 in 2020/21, to rise in line with inflation).
Changes to these amounts were recently announced in the March 2020 Budget. See also our the spring budget 2020 & your pension blog post.