As for somewhat informalinformal (and mostly brief) introductions to moduli spaces, see
Introduction to moduli spaces by Han-Bom Moon
The Moduli Space of Curves and Its Tautological Ring by Ravi Vakil in the Notices of the AMS
An introduction to the moduli spaces of curves by Maarten Hoeve
Rational Points on Moduli Spaces of Curves by Dave Jensen
A minicourse on moduli of curves by E. Looijenga
See also the BAMS paper Perturbations, deformations, and variations (and ``near-misses") in geometry, physics, and number theory by Barry Mazur, in particular, Sections 4 and 5.