The word geysir (or as written in English, geyser) originates in Iceland with Geysir, as it is called, being the first geyser known to Europeans. So without knowing your may have been using an Icelandic word for a long time. The origin of the word is "geysa" which means "to gush". Located in the valley Haukadalur, just south of Gullfoss waterfall. The oldest sources which mention hot springs in this region can be traced back to 1294, when they were activated by an earthquake. According to some research it has been active for about 10 000 years. While the old Geysir is inactive, Strokkur, which is also located in the Geysir area spouts every 5-10 minutes, with the water reaching about 15-20 meters from the ground. The old Geysir was apparently able to reach up to 170 meters, but research done in 1846 showed that it reached about 50 meters, which still is very impressive. The old Geysir has decreased in activity and until a few years ago it was aided by adding soap. This practice was stopped due to environmental concerns.
The entire area is very active and you will see a lot of water right next to your path. For your own safety be careful since the water is usually boiling hot. There are small warning signs but there is no real barrier to preserve the natural appearance of the area. The entry is free since the area is public even tough a few years ago there was an attempt by adjoining landowners to charge visitors. This was quickly revoked since the jurisdiction over the area was not clear.
Opposite of these natural wonders you find a big service area, It includes restaurants, a hotel and a store where you can purchase souvenirs and other memorabilia. It of course is also possible to purchase useful equipment and clothing in case you were not entirely prepared for the Icelandic weather. One attraction in the service center is a multimedia show on Icelandic phenomena such as the Geysir or the northern lights. An ideal place to warm up on cold days whilst learning more about Icelandic nature. Most golden circle tours have their lunch break either here or at Gullfoss waterfall.
Geysir is part of the so called "Golden Circle Day Tour", which is feasibly completed in eight hours from Reykjavik. It never fails to stun its visitors with its beauty. The tour also includes a visit to Gullfoss waterfall which is only ten minutes away and Þingvellir.