Shaykh Saalih Aalus-Shaykh said:

So Ahlus-Sunnah wal Jamaa'ah, this word was coined at the end of the second generation after Hijri by the followers of the narrations [Aathaar], and the opponents to the various sects that left the way of the companions [Sahaabah] and their students [Taabi'een].

And the first to use it [terminology] were some of the teachers of Al Bukharee - rahimahumuAllaah - and they joined the two words as-Sunnah and al-Jamaa'ah because there are those who call towards following Sunnah but they might not be with the Jamaa'ah. And there are those who call towards Jamaa'ah without following the Sunnah.

So the differenciation of the way of the people of Hadeeth and narrations [Athar] and the followers of the pious predeccessors [Salaf-us-Saalih] is based upon two things:

"Following the Sunnah and the Jamaa'ah"

And each from both of these is bound to the other.

So following the Sunnah is following the Jamaa'ah and following the Jamaa'ah is following the Sunnah; because it has been authentically reported from the Prophet - sall-Allaahu 'alayhi wa sallam - the narration which is in the 'Sunan', that he said:

"And this nation will split into seventy three sects. All of them are in the hell fire except one and that is the Jamaa'ah."

And [speech unclear] sects in the hell fire - meaning - that are promised with entering into the hell fire, and the victorious is only one sect and that is the Jamaa'ah. And they are the followers of the Sunnah, exemplifying the saying of the Prophet - sall-Allaahu 'alayhi wa sallam

"Upon you is my Sunnah and Sunnah of the rightly guided Caliphs, those who guide to righteousness, after me. Hold on to it and bite upon it with your molars" - The Hadeeth