思う is a ごだん (Type I) verb meaning to think or to feel. It is primarily used for subjective opinions, emotions, or intuitive thoughts. It is distinct from 考える, which refers to logical, analytical, or deliberate thinking.
That is how Fuguro works. It brings 思う back for review right before you forget it, each time a little later, until it sticks for good. You hear it spoken aloud, and you meet it again in stories you can already read. The first five levels are free.