There are six famous collections of the Holy Prophet’s (D.) traditions that are collectively known  as Sahah-e Sittah. The most authoritative two collection, which are jointly referred to as the “saheehain saheeh meaning correct. The term saheeh signifies that the said Hadith / Hadis is without any hidden imperfection, chain of transmitters is continuous up to sahabah-e kiram ascribing to Prophet (D. ) not disagreeable to trustworthy persons and repeatedly narrated by numerous pious and religious persons (deendar) and persons of abstinence (Parhezgar)
1.    Saheeh Bukhare (Jama-al Bukhare)
2.    Saheeh Muslim.

The other four collections are:

3.    Sunan Abu Daood
4.    Sunan Ibn-e Majah
5.    Sunan Nasaee
6.    Sunan Tirmize (Jama-al Tirmize)