This is Pro Mini 5V/16MHz is a 5V Arduino running the 16MHz boot-loader. Pro Mini ATMEGA328P come without connectors.
It’s a great board that will get you up and running quickly. The Arduino Pro series is meant for users that understand the limitations of system voltage (5V), lack of connectors, and USB off board.
The Pro Mini is a micro-controller board base on the ATmega328. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, an on-board resonator, a reset button, and holes for mounting pin headers.
A six pin header can be connected to an FTDI cable to provide USB power and communication to the board. The Pro Mini Arduino is intended for semi-permanent installation in objects or exhibitions. The pin layout is compatible with the Mini Arduino.