As Jessie says, it is indeed easier to understand when thinking in terms of pairs, in this case, by contrast with -ít. I would like to add to what she wrote that with the verbs in -ul/-ül the action is sort of made by the subject on itself, wherease with -ít the same action is performed by someone else.
Let's see with two examples: (A) tanulni vs tanítani, and (B) mozdulni vs mozdítani.
In (A), the 'action' is about 'bringing knowledge'. If a person does it on themselves, that is to say, 'learns' then we use the verb 'tanulni'. If a person bring the knowledge onto another one, that is to say, teach them, then we use tanítani.
In (B), the 'action' is about 'moving'. Funnily enough, we use the same word in English ('The table moves', something you can say during a spiritism session, or 'I moved the table'). In Hungarian we make the difference (you can guess which one is which).