The hotspots are regions, where the plumes of magma are present just below the lithosphere. The plume of the magma is the particles of the volcano and the gases, which is erupted during the volcanic eruption. It is generated by the fragmentation of the magma. Once, it reaches the lithosphere, it get spreaded laterally.
The plumes at the hotspots are present just below the tectonic plates, a high temperature r heat and the low pressure causes the rocks present in the lithosphere to melt resulting in volcanic eruption. At hotspot, the melting of rock takes time, sometimes it is very slow, due to the presence of various tectonic plates. Hence, the plumes can remain stationary for a very long period of time without erupting.
So, the first blank can be filled with Lithosphere and the second blank can be filled with Stationary.