Starting with the crux of this matter: There is absolutely NO difference between a Prophet (Nabi) and a Messenger (Rasool). It's simply an aspect of grammar and vocabulary concerning which traditionalists as well as so-called modernists, like a bunch of bratty clowns, have raised a storm in a teacup.
The Noble Quran asserts ::
"Muhammad is not the father of any one of you men; he is Allah's Messenger and the seal of the prophets: Allah knows everything." (33:40) Noble Quran.
We watch and hear plenty of our Muslim brethren, many of them supposed intellects with inflated egos, talk tirelessly about the difference between a Prophet and a Messenger. Often their arguments / discussions get lengthy and complicated. Ironically the matter is much too simple. There is absolutely NO difference between the two. When Allah The Almighty chooses a worthy person by inspiring him to deliver His Message, the occurrence makes that person a Prophet. Subsequently, when Allah bestows His Message on that person commanding him to deliver it to humankind, that mission makes the Prophet a Messenger by definition of every language.
There are also some angels that are referred to as "rasools" (messengers). Why? Because they carry out the commandments of Allah from the Heavens to the earth. Obviously there cannot be prophets among angels because angels are created by Allah only to obey His orders; unlike humans on whom Allah has bestowed the ability to choose their path of conduct - obedience or disobedience to His orders. Thus, to deliver the Message & Guidance of Allah to all of humanity, Allah decided to choose certain humans who were worthy of this task .. those whose strength of character made them superior to the rest of their contemporaries during their era. The choice of Allah in selecting that special person to deliver His Message is called Prophethood, giving that person the status of a Prophet. But no Prophet was ever chosen to sit idle. The very purpose of The Almighty for choosing a Prophet was to place upon him the responsibility of conveying the Divine Message (through Divine Revelations). That responsibility bestows the status of Messengership on every Prophet.
Hence, every Prophet must be a Messenger, and every Messenger must first be a Prophet (that is, a person chosen by Allah). Needless to say, Allah Almighty does NOT vouchsafe the duty of delivering His Message to just any average 'lunchbucket Joe.' As Allah confirms in His Most Noble Message: "Allah knoweth best with whom to place His Message." (6:124).
This wrangling between the definitions of prophet and messenger began in the 1980s when an Egyptian pharmacist turned apostate named Rashid Khalifa claimed he was a "messenger" of God. Referring to Verse 33:40 (quoted in the beginning of this blog entry) Khalifa and his small band of supporters misinterpreted the Verse claiming it only confirms that Muhammed (pbuh) is the last Prophet, but not the last messenger. Many within the so-called Progressive Muslims group also accept Khalifa's claims. Of course, it goes without saying that the claim is patently false. Verse 33:40 plainly conveys the information that after Muhammed (pbuh), Allah does not intend to choose any one for the same mission, which automatically puts an end to the coming of any future messengers.
In response to Khalifa's followers, the traditionalists prepared their own argument saying every messenger must be a prophet (which is correct), but every prophet is not necessarily a messenger (which is not correct). To this, the rejoinder of the Khalifites was the opposite, as expected, saying while every prophet must be a messenger, every messenger does not have to be a prophet. And therefore they claimed, Rashid Khalifa was not a prophet but a messenger.
Then the traditionalists expressed a concept that a prophet is one who may not necessarily receive a Divine Scripture while a messenger always received Divine Revelations in the form of a Scripture. Again as expected, the Khalifites did not agree because Rashid Khalifa had nothing to show which he could claim as a Divine Revelation to him.
Definitely, the squabbling was initiated by the Khalifites and they were fully on the wrong path. The traditionalists too haven't been insightful with their responses. Verse 33:40 asserts without a doubt that Muhammed (pbuh) was the final Prophet and consequently the final Messenger as well. Instead of simply adhering to this Verse and rejecting all arguments of Khalifa supporters, the traditionalists began weaving their own counter-argument which was just as discrepant as that of their opponents. There's no such thing as a prophet not receiving a Scripture. As already highlighted, Allah had a purpose for choosing every Prophet, commanding him to convey the Divine Messages to mankind. Those messages were sent in the form of Revelations later compiled into a Scripture. No Prophet was ever chosen without a goal.
Except for the Quran, all former Messages have either been lost or altered by human hands. The Message of the Quran is the only Divine Revelation that is fully original and intact, and will remain so until the Last Day.