Those post from Bruce are very valuable. They show very simple methods to make you comms more robust.

Dhouston also has some very good information on similar subject: http://www.picbasic.co.uk/forum/showthread.php?t=6261

in lamen's terms how I can use CRC?
This is my best attempt to address this in particular (full disclosure - I am no expert). CRC is used in many places when you want to validate the contents of a packet (i.e. detect the packet to be error free). A packet can be anything: wireless data, ethernet data, bootloader data, archive data (read WinZIP). It is a very simple way of coming up with a somewhat unique identifier that tells you the packet you have has not been compromised (i.e. corrupted, changed, etc).

How effective is it? - It depends. There are as many algorithms (polynomials) as days of the year (and then some). It all depends on how "unique" you want to define your packet and how much math (read - computer resources) you want to use to come up with the CRC.

How simple is it? - Again, it depends.

Why use it? - It is pretty standard method of validating packetized data; as long as you have the computing power to do it, and select an algorithm/polynomial and stick with it.

What it does? - It gives you confidence on the validity of your packet (i.e. error detection).

What it does not do? - If your data packet is corrupted, it does not tell you how to correct it (i.e. it does not have error correction).

How you could use it? - On the transmit side, you calculate the CRC of your data packet (after selecting the algorithm you want/need) and send it along with your data packet (usually at the end). On the receive side, you receive the data packet and the CRC. Calculate a new CRC value form the data packet (not including the received CRC) and compare it to the received CRC. If they match you have a higher degree of certainty the packet is free from errors.

Good reads:
http://en.wikipedia.org/wiki/Cyclic_redundancy_check
http://www.hackersdelight.org/crc.pdf
http://www.repairfaq.org/filipg/LINK/F_crc_v3.html