First of all, do you understanding the definition and meaning of a customer relationship management (CRM)? CRM is a collection of processes that a company takes to ensure that they are building a positive relationship with their customers. Many times they will use a CRM software to help them. A CRM software can help a company keep track of:
-Customer's name
-Contact info
-Important dates
-Summaries of when they have been contacted
-Other important info
A company using good CRM techniques will always use some sort of CRM software and jot down all the notes they have taken when they have contacted their customer. Then the next time when the customer is contacted, the person from the company can easily pull up the customer's file and view all the notes and information taken while talking to the customer in the past. They will be able to see what was discussed and had happened without having to spend more time repeating the same things again. That way they can use the time saved to discuss other issues and help the customer better since they have a sense of what's going on already.
Also, some small examples of good customer relationship would be sending personal letters thanking them or wishing them well, such as during the holidays, on their birthday, or after a sale. Giving them a gift card or something small as a token of appreciation. Or giving them a regularly schedule call just to address any concerns they might have and keeping them updated.
As far as poor customer relationship, it's pretty much the opposite of what I previously mentioned. I'm sure you have experienced bad customer service before. What did you wish they did differently? With a proper CRM in place, companies should be able to take care of customers more efficiently.
Wikipedia has a god article about it: http://en.wikipedia.org/wiki/Customer_relationship_management
And another site I found wasn't too bad either: http://searchcrm.techtarget.com/sDefinition/0,,sid11_gci213567,00.html
Hope that helps.