What is a research proposal and what are the salient features/characteristics of a research proposal?

Research proposals will differ slightly from discipline to
discipline. However, there is enough overlap to make some general points. Also I should
say that the above answer makes some good points. 

First,
you should have a clear thesis or objective. You should be able to say what the project
or work will be about in a few sentences. 

Second, you
should also circumscribe the extent or boundaries of your proposal. No proposal should
be amorphous. So, set your boundaries and let your readers know
them. 

Third, you should give a historical overview of
where the state of affairs are in your field. In other words, an overview of the work of
others is important. 

Fourth, you should say a word about
your methodology and justify your proposal. In other words, why should your work
exist? 

Finally, you should have a brief roadmap of your
work and a working bibliography.