Four generations of iPad have been released as of 2012:
- ipad 1st generation
- ipad-2 2nd generation
- ipad-3 3rd generation (a.k.a. 'the new iPad')
- ipad-4 4th generation (a.k.a. 'iPad with retina display')
Unless your question is narrowly about one model and not the others (or not otherwise obvious, you can tag your question with iPad to get the widest audience for answers. Also, many questions about iPad issues could really be asked as ios questions if the issue relates more to the software than the particular hardware.