DCFL : One stack is enough to handle all comparisons between two variables : a$^n$b$^n$ type
CFL : More than one stack required for handling all comparisons between any pair of 2 variables : a$^n$b$^n$c$^m$d$^m$ type where one stack is for ab, one is for cd
CSL : Stack requirement for comparison of more than 2 variables : a$^n$b$^n$c$^n$ type
L1 falls in CFL category only, and by extension in CSL, REC/REL etc
