Hey, I'm relatively new to pedals, and I've heard a lot of experienced guitar players talk about "I have this pedal that I modded right out of the box." What does modding a pedal do? Is it easy? Is it necessary? What's the deal here?
modding just means 'modifying'

so if you have a pedal you can mod it by changing certain components to certain values to change the sound a certain way.

explaining 'what modding is' to you in a blanket statement is pretty hard. it's like customizing a car, for example.
if I've done custom work on my car, it could mean I put different rims on it. could mean I put a sound system in. maybe I did some engine work. see what I mean? it's just liek, the general term for altering a pedal in some way.

if you have a certain pedal and you want a different kind of sound out of it, there may be a way to mod it to sound the way you like..