means the drive was returned to the manufacturer, confirmed to have an error, and repaired.
means the drive was returned to WD, found to have no problems, and can be re-sold as being in working condition.
Recertification is what happens to many store returns, where the person either lied about the condition, or where the store has a policy to not re-shelf anything.
Walmart, for example, does not re-shelf anything. However, Walmart sends their returned goods back to their own warehouse facility, where it may be deemed okay and put back into stock. (At least, that's how it was at Walmart at one time, as recently as 2009, according to a local Walmart manager.)
Some companies bulk send everything back to the manufacturer, and let them sort it out. The retailer gets refunded -- in fact, there's a whole complex financial tier and book of policies, as it related to returns to manufacturer, by a store. (You'll notice some manufacturers have printed "Do Not Return to Store, Call Us at 1-800-HELP-ME" because they'll be penalized by going the long way for the return.)
I buy a lot of reconditioned, refurbished and recertified computer parts and electronics. If anything, I tend to have more issues with new/unopened products than one of the "re's". If the deal was good, and the cosmetic condition of the item is like new, I have no second thoughts about buying such merchandise. I buy a lot of used books and DVDs, too, assuming good condition (unmarked pages with clean covers, unscratched discs in clean cases).
Thrift is even one of those religious moral values!
$75 for 2TB is about $35 OFF for the EADS drive model. Assuming the seller has good feedback, I'd go for it. Buy it.