The 73 sects mentioned in the Hadith are detailed in Mawaqif of Hadhrat Idhhuddin Abdur Rahman bin Ahmad. There are basically 8 sects in Islam.
1. M’utazila. This sect believes that human beings are themselves the creators of their actions. They reject the vision of Allah Most High in the hereafter. They consider giving reward on good deeds and punishment on bad deeds as Wajib on Allah Most High. There are 20 sub-sects of this sect.
2. Shia. This sect crosses the limits of propriety of love of Hadhrat Ali (May Allah Most High be well pleased with him). This sect has 22 sub-sects.
3. Khawarij. This sect disrespects Hadhrat Ali (May Allah Most High be well pleased with him) to the extent that they declare Hadhrat Ali (May Allah Most High be well pleased with him) as a disbeliever (May Allah Most High protect us from this). They consider someone who commits a major sin (Gunah Kabira) as an apostate. This sect has 20 sub-sects.
4. Murjiya. This sect believes that disobedience is not harmful along with Iman as obedience is not beneficial with disbelief. This sect has 5 sub-sects.
5. Najjariya. This sect's beliefs about acts of the creation are as per the beliefs of the Ahle Sunnah, but in other details of the faith, they follow the M’utazila, such as that Allah Most High has no attribute, the Word of Allah Most High is created and not eternal (may Allah Most High protect us from this). This sect has 3 sub-sects.
6. Jabriyya. This sect believes that human beings are under absolute compulsion. They don’t have any freedom to act. This is only one sect. It has no other sub-sects.
7. Mushabbiha. This sect believes that in having a physical body and in being able to enter a particular place, Allah Most High is similar to human beings. This sect has no sub-sects.
8. Ahle Sunnah. This is the sect, which is truly guided and which will be delivered. The Holy Prophet (Sallallahu alaihi wa sallam) said: The sect, which will be granted deliverance is the one, which is on my path and the path of the Companions.
The beliefs of this sect has free of innovations and false notions. This sect is free of all extreme beliefs and is perfectly according to the Holy Quran and the Hadith.
(Mawaqif of Hadhrat Idhhuddin Abdur Rahman Bin Ahmad, Maqsad Us Sabe’; Mirqaatul Mafateeh, Kitab Ul Iman, Babul 'Itisaami Bil Kitabi Was Sunnah)