Please explain the various categories of defects?

Following are the three primary categories of software defects:

• Wrong – Results when there is a deviation from the given specifications. This type of defect occurs when requirements are implemented incorrectly.
• Missing – This happens when customer specifications are missed, i.e., they are not implemented. This might also happen when customer requirements are not clear but implemented.
• Extra – Caused by requirements that are implemented but are not provided by the customer(s). Although this type of defect is variances from the customer specifications, they might be desired by the end-users.