A Gazette is an Official record book where all special government details are spelt out, detailed and recorded. A Gazette will show the communities or villages that have been granted excision and the number of acres or hectares of land that the government has given to them.
A community or individual with a Gazette document can only sell lands within the area that was excised by the government to them. If later on the government decide to acquire you land for some reasons or particular project, you will be entitled to a compensation as long as the land is within the excised portion that was given to that individual (indigene of a community). The best way to confirm for the authenticity of a land that has been covered by a Gazette is to get a certified surveyor to chart the site and take it to the surveyor general office of that state to get the accurate land information so as to know if the land falls within the Gazette and spell out which location it can be found.
NB: A Gazette is a very powerful instrument the community owns and can replace a Certificate of Occupancy to grant title to the Villagers.