Normally you can use either set of the operators but it is not recommended to mix them in the same expression. The difference between the two sets is the precedence. The operators that are words (and, or, not) are lower in the operator precedence table than the other three.

Logical operators are used in a conditional expression, for example in an if statement or in the Ternary operatory, we would like to combine 2 ore more conditions.

For example we would like to check if the age of the user is bigger that 18, but smaller than 23.

We can write:

18 < age and age < 23

The same can also be written as

18 < age && age < 23

There is no real difference between the two expressions. The && are there mostly for historical reasons as they were used in many programming languages before Ruby. and is usually much more readable.

examples/ruby/logical_operators.rb

if ARGV.length < 1
   puts "Needs an argument for age"
   exit
end

age = ARGV[0].to_f

if 18 < age and age < 23
    puts "In the range"
end


if 18 < age && age < 23
    puts "In the range"
end