Nevermind, I figured it out. Apparently the "=>" is a way to define functions. This is the resource I used if you also want to learn.

I'm a beginner, and in the tutorial, there is this part:

var targets = creep.room.find(FIND_STRUCTURES, {
  filter: (structure) => {
  return (structure.structureType == STRUCTURE_EXTENSION || structure.structureType == STRUCTURE_SPAWN) &&
  structure.store.getFreeCapacity(RESOURCE_ENERGY) > 0;
}

and it's really confusing me. I don't get what format they want, what the => is for, and why it needs to return a value. If someone could break down the components that'd be greatly appreciated!