Rambam- Yisdoei HaTorah Perek 7 Halacha 3: Examples of Parables That Were Given to Prophets

הדברים שמודיעים לנביא במראה הנבואה דרך משל מודיעין לו ומיד יחקק בלבו פתרון המשל במראה הנבואה וידע מה הוא. כמו הסולם שראה יעקב אבינו ומלאכים עולים ויורדים בו והוא היה משל למלכיות ושעבודן. וכמו החיות שראה יחזקאל והסיר נפוח ומקל שקד שראה ירמיה והמגלה שראה יחזקאל והאיפה שראה זכריה. וכן שאר הנביאים. מהם אומרים המשל ופתרונו כמו אלו. ויש שהן אומרים הפתרון בלבד. ופעמים אומרים המשל בלבד בלא פתרון כמקצת דברי יחזקאל וזכריה וכולן במשל ודרך חידה הם מתנבאים: 

The things that are made known to a prophet in a prophetic vision are made known to him (or her) through a parable. Immediately, the interpretation of the parable is given in the prophetic vision and [the prophet] knows [the interpretation.] For example, the ladder that Yaakov, our forefather, saw and the angels were ascending and descending on it and it was a parable for kingship and servitude (Bereishis 27:10-15). More examples are the beasts that Ezekiel saw (Ezekiel:1), the bubbling pot and staff [made from] an almond tree that Jeremiah saw (Jeremiah 1:11-14), the scroll that Ezekiel saw (Ezekiel 2:9), and the Ephah (Rashi says this is a large measuring vessel) that Zechariah saw (Zechariah 5:6). Also, by other prophets some would relate the parable and the interpretation like these [previously mentioned prophets] and some would relate the interpretation alone. There are times prophets would only relate the parable without the interpretation like some of the words of Ezekiel and Zechariah. All [the prophets] had prophecies through parables and puzzles (except Moshe as will be discussed at the end of this section in the Rambam).              

 This is a description of how prophecy is given over. G-D does not just talk to man, He relates ideas to man through imagery that can then be understood as a particular message. Yaakov understood the ideas that G-D was trying to convey only through the imagery of angels ascending and descending. G-D did not (could not?) communicate with Yaakov directly and say, "Hey Yaakov, just wanted you to know that your kids are going to have a glorious kingdom, but then be scattered throughout the world in servitude." As we will see later, that only happened (was only possible?) with Moshe.