An eARC is an electronic Advance Reader Copy. This is an unproofed manuscript and is guaranteed to be full of typos and error. It is pretty much raw from the authors word processor. But you get the entire eARC well in advance of even the Monthly Baen Bundle release.
Please do not send in typos and errors, we know the eARC is unproofed and the author doesn't need to be inundated with "corrections".
ARCs do not include the final proofed version. For the final version you would have to buy the single or monthly bundle for that book.