What is peripheral module function??

Marlene said:

When PxSEL=1 --> Pin function: Primary peripheral module function is selected.

Most pins of the MSP430 are multiplexed with more than 1 functionality. By default most pins are GPIOs, so the peripheral functionality would be to switch that pin from it's default GPIO state to a function used by a peripheral (for example SPI lines, Timer outputs, etc). Please refer to the beginning of the datasheet to see the peripheral functions for all the pins of the MSP430.

Marlene said:

What is the difference between module enable(ME) and interrupt enable(IE)?

A module enable will enable a peripheral as a whole to function, such as a serial communication peripheral. An interrupt enable, will allow the given peripheral to trigger an interrupt provided general interrupts are enabled. If the interrupt enable is not set for a given peripheral it can run, but it cannot trigger interrupt events.