Hii Irshad,

GD means Group Discussion. Generally GD and PI  is conducted for Admission process for colleges and in campus placements. 

GD is all about how you deal with the Team and share your ideas effectively. In this they will test your Leadership skills, Managing skills and patience.you will be given a topic and in a group you have to share your ideas and also listen others ideas and finally all should come to a conclusion on one point.

Generally in any interview, Every HR tests how confident you are ? and how much communicative you are ? You should sell yourself to the interviewer. The most commonly asked questions in a interview are 

• Introduce yourself
• Why should I hire you?
• What are the extra skills you have?
• Expected salary package?

Thank you