cifs
CIFS is roughly the same as SMB version 1 (it's more complicated than that, but they're close enough for our purposes). Apple's implementations of SMB version 2 (introduced in OS X v10.9) and version 3 (OS X v10.10) were a bit buggy, at least at first. If you use an "smb://" URL in the connect dialog, it'll use the newest version that both the server and client support, and if you're still seeing weird behavior from that... then you can use "cifs://" to force it back to the old version 1 protocol, which might fix it (see e.g. this ZDNet article, which also gives a way to force version 1 via the nsmb.conf file).
If you aren't having trouble with the newer version of the protocol, or you are but switching back to the old version doesn't help, then use "smb://" -- the newer versions of the protocol are significantly faster and generally better.
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