Extended storage phones, like your Note 2, connect using a Microsoft protocol called mass transport protocol, MTP, rather than the older USB mass storage protocol to get to the built-in storage. Linux and Macs lack native support for that, so with a Mac you could add it with Android File Transfer - that was developed by Google as a generic solution beginning back with Honeycomb.
Two problems. Over time, Samsung has and hasn't been dead on in following the MTP spec, so that's led to issues. Now that they seem ok (as far as I know today), Apple's latest OS X isn't happy with Android File Transfer with many devices. (AFT seems to work fine up through Snow Leopard.)
Keis is purpose-built by Samsung to provide full connectivity to Samsung phones.
If Keis gives you trouble with your setup, you might try some of the wireless solutions. AirDroid is easy, free and works very well, for example.
Hope this helps!
