This is, essentially, a low-cost endowment but with premiums starting at a low level and rising gradually over a number of years to the full premium.
This type of policy is aimed at the house buyer who is working on a very tight budget but who has expectations of pay rises in future years.
The initial premium is very low but this is balanced by a full premium which is somewhat higher than that for an ordinary low-cost endowment for the same sum insured.