"3+2BCP" What is this?

Was about to put an order in for the X270, when I realised I didn't have a clue what the merits of the different options were.

For Instance:

• 3+2BCP, Fingerprint Reader, NFC, PCIe

Is this an external PCIe slot?, like for use with a docking station or is it something internal?

• 3+2BCP, Fingerprint Reader, NFC, SATA

A SATA port?, Is that eSata or an additional one internally?