difference between for and each in ruby

hoge.rb

 # -*- coding: utf-8 -*-
a= [1, 2, 3]
for v in a
  b = 'a'
  puts v
end
puts b

a.each do |v|
  c = 'a'
  puts v
end
puts c


------------------------------
1
2
3
a
1
2
3
hoge.rb:12: undefined local variable or method `c' for main:Object (NameError)