This is a pro-purchaser agreement between two companies.
It relates to the sale and purchase of land whose tenure is leasehold, meaning that the vendor holds/owns the land for a limited period of time subject to payment of annual rent as compared to a fee simple/absolute tenure which has no such term and rent limitations.
In many cases, the lessor is normally the Government of Kenya. However county governments, as well as private individuals and entities, also lease out land subject to certain conditions. The title document in question will normally guide as to who the lessor is and what the terms, such as rent payable, are.