Hello Simon,
With all due respect it really doesn't matter if you understand
this unless you are involved as a potential investor/buyer.

i am doing this to protect other people to get in same situation

For the benefit of those not involved but curious.
A caution is a legal document registered at register of lands served to parties similar to a cease
and desist order.

In this case papers were duly served, there is a lien placed on the
property and no work should be undertaken until the matter is legally
resolved in front of a Magistrate.