Quick Answer

Blocks are anonymous functions that can be passed to methods.

Understanding the Issue

Ruby blocks are chunks of code between do/end or curly braces {}. They can be passed to methods like each, map, etc. and executed with yield.

The Problem

This code demonstrates the issue:

Ruby Error 
# Problem: Inefficient iteration
[1,2,3].each do |n|
  puts n * 2
end

The Solution

Here's the corrected code:

Ruby Fixed 
# Solution 1: Using blocks
[1,2,3].map { |n| n * 2 }

# Solution 2: Custom block method
def triple
  yield * 3
end
triple { 5 } # => 15

Key Takeaways

Blocks enable powerful functional programming patterns.