A Will differs from a deed in the following respects: (i) a deed operates eo instanti, i.e., from the date of its execution; a Will comes into operation on the death of the testator; (ii) a deed is ordinarily irrevocable, unless there is an express power of revocation; a Will can be revoked at any time by the testator during his life time. It is ambulatory and it becomes effective and irrevocable