It is process which examines and decided the current market value of the property on the basis of several factor like- demands & supply, property size, construction quality, location and connectivity etc.
It is important because it will give you a clear idea of your property's current net-worth. This could be useful at the time of applying for some loans or while selling the property.
It is a property for which the lessee owns temporary ownership (for a fixed period of time) and after the completion of time, the property goes to its original owner/lesser, until the contract is renewed.
A property, whose ownership rights are completely given to the purchaser, is termed as freehold property.
It is always advised to convert a Leasehold property into a Freehold property because you will become the sole owner of it. For this you need to get the sale-deed and get the property registered on your name.