Rasool is the messengers, the person who is sent by Allah for an Ummah (community) or for the greater part of humankind as a prophet with a book and Shariah (law). Nabi is prophets, the one who acquires message. They do not accompany any book along with them or law but they execute the systems of prophets previous to them. The Quran has used both the words, Nabi and Rasool, which reveals that there were two sorts of messengers. The majority was Nabi only and others were both Nabi and Rasool.
Hazrat Noah (A.S) was a Rasool (prophet), sent to advise mankind of that area and his people to modify their habits. Noah A.S. started teaching to his people both orally and physically. He constantly warned the individuals about the situation, truth, and right path and requested them to accept one God instead of worshipping idols. He called the individuals to serve God and said that no one would spare them except the one God, Allah. Both Noah A.S. and Ibrahim A.S. were taught the prophet hood and the scripture. There are few very prominent differences between the two. The distinction between Rasool and Nabi is;
1-A Rasool was a person who was provided with another Sharia (codes for law) by Allah, starting from Him. A Nabi was also a messenger of Allah but he was not provided with a new or fresh Shariah instead he continued to preach the Shariah of previous Rasool. Although, there are some Rasool which did not bring any Sharia e.g. Hazrat Isa A.S. (Jesus) followed the Sharia of Hazrat Mousa A.S.
2-Sheikh Mufid, an incredible researcher for Islam composes in his book, Awa’il al-Maqalat that every messenger is a prophet [Nabi], but not every Prophet is a Rasool [Apostle]. Consequently, all Rasools were Nabi but the greater part Nabis were not Rasools.
3-A Prophet is constantly a Nabi by birth; however, a prophet gets Risalah (becomes Rasool) when he authoritatively receives the post during his life. Our Prophet Muhammad S.A.W was bestowed upon Risalat when He was at the age of 40.
4-A Rasool receives the message from the Almighty Allah in unlike ways such as dream while sleeping, or direct contact with Holy messengers when he is awake. He can witness and chat with the Holy angels during contact of the divine message. But a Nabi [prophet] varies from the Rasool, in that he doesn’t witness the Holy angels when he is up but only noticed during sleep.
5-A Rasool is greater in grade than a Nabi.
6-There has been no case reported in the history of mankind where a Rasool was killed by non-believers. However, there are several cases when Nabis were killed by non-believers.