“Does the iPad have built-in speakers or do I need headphones to use it?”
The iPad includes built-in speakers on every WiFi and 3G model. As long as you are in a quiet space with little external noise, the speakers work well for watching movies downloaded from iTunes or streaming on Netflix. If you are somewhere noisy, like on an airplane or commuting to work on a bus or train, you will probably want to use headphones instead.
The iPad does not come with headphones. You either need to purchase them separately or Apple may assume you will use the ones that came with your iPod or iPhone. For most situations, I would recommend either plugging in headphones or using external speakers with your iPad. In public spaces, you avoid annoying people around you by using headphones. At home or in your office, you have greater control over the sound if you use the headphone jack instead of onboard speakers.