When we were at the visitor's center I was primarily interested in taking photos of the petroglyphs. Later I got a chance to walk to the trail and see them in person. I was also interested in the exhibits on island formation but I didn't take photos of them.
Kilauea Visitor Center should be your first stop after entering Hawaii Volcanoes National Park. You can find out where lava is flowing, updates on park closures, and other important info. There were some exhibits about the volcanoes, a gift shop, and the largest set of restrooms in the park. Open 7:45 am-5 pm daily. Something we found especially neat is that you can bring your own water bottle and refill it with rain water “captured from the clouds, filtered by sand, and pumped by solar” for free. Photo of the water refilling station. If you didn’t bring your own bottle, you can buy one from the gift shop.
The Visitors Center is the first place you'll come to when entering. It isn't compulsory to visit but it would be advisable to stop in and get some history before going any further in the park. Here you can pick up hiking maps, watch a history movie, buy souveniers, get water, and view the exhibits.