Data Quality (DQ) is a concept and a business term covering the quality of the data used for a particular purpose. Often times the DQ term is applied to the quality of data used in business decisions but it may also refer to the quality of data used in research, campaigns, processes and more.
Working with Data Quality typically varies a lot from project to project, just as the issues in the quality of data vary a lot. Examples of data quality issues include:
A less technical definition of high-quality data is, that data are of high quality "if they are fit for their intended uses in operations, decision making and planning" (J. M. Juran).
Data quality analysis (DQA) is the (human) process of examining the quality of data for a particular process or organization. The DQA includes both technical and non-technical elements. For example, to do a good DQA you will probably need to talk to users, business people, partner organizations and maybe customers. This is needed to asses what the goal of the DQA should be.
From a technical viewpoint the main task in a DQA is the data profiling activity, which will help you discover and measure the current state of affairs in the data.