In Ruby, `map` and `each` are two different methods used to iterate over collections such as arrays or hashes. Here's a breakdown of the differences between them:

1. Purpose:
   - `each`: The `each` method is used to iterate over a collection and perform an operation for each element. It is primarily used for side effects (such as printing to the console or modifying external variables) and does not produce a new array.
   - `map`: The `map` method is used to iterate over a collection, apply a transformation to each element, and return a new array containing the transformed elements.

2. Return Value:
   - `each`: Returns the original collection.
   - `map`: Returns a new array containing the results of the block's execution.

3. Usage:
   - `each`: Typically used when you want to perform some action on each element but do not need to collect the results.
   - `map`: Used when you need to transform each element of the collection and collect the results into a new array.

Example

Using `each`:

numbers = [1, 2, 3, 4, 5]
numbers.each do |number|
  puts number * 2
end

Output:

2
4
6
8
10

The original `numbers` array remains unchanged, and `each` returns the original array.

Using `map`:

numbers = [1, 2, 3, 4, 5]
doubled_numbers = numbers.map do |number|
  number * 2
end
puts doubled_numbers

Output:

[2, 4, 6, 8, 10]

The `map` method returns a new array (`doubled_numbers`) containing the results of the block's execution.

In summary, use `each` when you need to iterate over a collection for side effects, and use `map` when you need to transform each element and collect the results.