The Quran contains two types of knowledge: revelation and inspiration.

Revelation is a type of Quranic knowledge that is unique to prophets; however, the Imams, who are the successors of the Holy Prophet Muhammad, receive Divine inspiration; other pious people can also receive this, though the Imams receive the highest form of it, while non-infallibles receive it to a lesser degree and to varying degrees depending on their status. 

The Quran's Knowledge Types: Revelation

It is not [possible] for any human that Allah should speak to him except through revelation or from behind a veil, or send a messenger who reveals by His permission whatever He wishes. Indeed He is all-exalted, all-wise.
This verse explains the three ways God communicates with His prophets:

Direct revelation without the use of an intermediary
Revelation from behind a veil, such as when God spoke to Prophet Moses (peace be upon him) through the tree or when the prophet is in a dream state.
Revelation by an Angel 19
The entire Quran was revealed to the Prophet, and God also spoke to the other Prophets through revelation. This knowledge comes from a Divine source.

The Quran's Knowledge Types: Inspirational

We revealed to Moses’ mother, [saying], ‘Nurse him; then, when you fear for him, cast him into the river, and do not fear or grieve, for We will restore him to you and make him one of the apostles.’ 20
Although the translator has translated the word way () as revelation, it does not refer to the terminological meaning as that which is revealed to prophets, but rather to inspiration into the heart.

The distinction between revelation and inspiration is that revelation is unique to prophets while inspiration is not. Second, revelation is continuous, whereas inspiration is sporadic. Third, as mentioned in other verses, inspiration can come from inanimate objects such as the sky 21, as well as insects such as the honeybee 22. It refers to the natural instinct in this case. Inspiration is not always divine and can be satanic as well.