The Arduino Pro is targeted for more advanced users while keeping the price down by keeping only the minimum required component on board.
It is based on the ATmega328P operating at 16 MHz. Arduino Pro pinout includes 14 digital I/O pins, 6 analog inputs and 6 PWMs. It has 32 Kbytes of Flash, 2 Kbytes of SRAM and 1 Kbytes EEPROM.
The peripherals include TWI (I2C), SPI, UART and 10-bit ADC. As shown in Arduino Pro Mini Pinout, it doesn't have any port to connect to. So an external USB to serial adapter is needed to program it.