The lava flow that you are walking across consists of a type of lava known by the Hawaiian name as pāhoehoe lava.
Hawaiian volcanoes erupt two types of lava, pāhoehoe and ʻaʻa. The terms pāhoehoe and ʻaʻa were the words used by native Hawaiians for these two types of lava flows. Geologists in Hawaii adopted these terms in the 1800's and they are today used by scientists internationally.
Pāhoehoe is basaltic lava that has a smooth, billowy, undulating, or "ropy" surface. These surface features are due to the movement of very fluid lava under a congealing surface crust.
ʻAʻa is basaltic lava characterized by a rough or "rubbly" surface composed of broken lava blocks called clinker. It is much harder to walk across an `a`a lava flow.