Question

What is the meaning of the existence of a large $N$ limit in QFT?

Answer 1

Explanation:

The 't Hooft limit of 4-d ${\cal N} =4$ super-Yang-Mills at the conformal point is shown to contain strings: they are IIB strings..

Answer 2

Explanation:

Its spectrum is the set of possible outcomes when one measures the total energy of a system