What does ||= (or-equals) mean in Ruby?

Question

What does the following code mean in Ruby?

||=

Does it have any meaning or reason for the syntax?

Answer 1

irb(main):001:0> a = 1
=> 1
irb(main):002:0> a ||= 2
=> 1

Because a was already set to 1

irb(main):003:0> a = nil
=> nil
irb(main):004:0> a ||= 2
=> 2

Because a was nil