Memorandums of Encumbrance's are common in Land Divisions and are an agreement in favour of the Developer constraining the owner of the land.
No two encumbrances are the same but usually include restrictive covenants which maintain uniformity within the division eg. colour and type of fencing, house design etc.
Land being purchased in a new development may require a "new encumbrance" to be lodged at settlement.
An encumbrance may be registered on the Certificate of Title for the land (improved/unimproved) you are looking to purchase this encumbrance may require a "lift and replace" or "run" with the land.
Optima are happy to answer your queries regarding any encumbrance mentioned in your contract.