Pillow lava is part of a sequence of rocks called Ophiolites. These were originally molten rocks from beneath the ocean that have later become exposed to the surface.
Pillow lava is a very hard rock with a high mineral content. The Pillow lava in Oman originally formed on the floor of a deep ocean. As underwater volcanoes pushed out molten rock along cracks in the sea bed, the lava quickly solidified under the great pressure and coldness of the ocean depths. The resulting rock pillows look a little like toothpaste squeezed from a tube.
Another part of the sequence that can be seen here are sheeted dykes; look for a layer of rock beneath, where shiny minerals are oriented in the same direction.
On top of the pillow lava, the shale that was once deposited when the ocean covered it has been moved to another place. Instead a wadi developed leaving gravel sediments.