There is a difference between the people of knowledge regarding the difference between the two.
That which is popular amongst the people of knowledge is that a Nabi is a person who is inspired with a Law but has not been ordered to spread it among the people. Instead, it has been inspired to him that he should do such and such an act such as Pray in a certain manner and Fast in a certain manner but he has not been ordered to command the people to perform these acts in the manner they have been inspired to him.
However, when a person has been inspired by God a Law and has been ordered not only to perform it by himself but also order the people to perform and observe the Laws then he becomes a Nabi and Rasool such as Muhammad (PBUH), Eesa, Mosa, Nuh, etc.
And according to the other thought which is present among the People of knowledge a Nabi is one who has been given a Law (Sharia) which is not completely independent but follows and adds to the Law (Shariah) given to a Nabi before him. And if he has been given a Law (Shariah) which is completely independent from the one of a Nabi prior to him then he becomes a Nabi and a Rasool.
For example, Mosa was given the Torah which was an independent Law so he was a Nabi and a Rasool, but a number of Nabi came after him with Laws which were in accordance with the Torah and were not entirely independent so they all were Nabi not Nabi and Rasool.
These are the two opinions among the People of Knowledge
Source:
Ø§Ù„ÙØ±Ù‚ بين النبي والرسول |](ما الفرق بين النبي والرسول؟ - موقع الشيخ ابن باز).
ÇáÝÑÞ Èíä ÇáäÈí æÇáÑÓæá - ÅÓáÇã æíÈ - ãÑßÒ ÇáÝÊæì](إسلام ويب - سعادة تمتد)