In the literature, there are many theories and quantities which I usually seen in the context of conformal field theory that described via the notation of $(a,b);\quad a,b\in\mathbb{Z}$
for example:
6 dimensional (2,0) superconformal field theory (6D (2,0) SCFT)
deforming $\text{CFT}_2$ by a (2,2) quasi-primary operator.
(NS,NS) sector of superstring theory is given by vertex operator in the (-1,-1) picture
what this notation $(a,b)$ is stand for? I know that in $\text{CFT}_2$s the Virasoro generators are coming as two copies one for the right sector and the second for the left sector. Is $a$ representing the number of extended supersymmetries in the left sector while $b$ on the right? if so, what are (2,0) represents in the first example treating 6d $CFT$?
