Rake is a Ruby task management tool. Like in Unix we have 'make' utility.
So we can say Rake is Ruby Make. It uses a Rakefile and .rake files to create a list of tasks.
We can see all the Rake tasks available in our current directory by one of the below commands in terminal:

rake --tasks
rake -T

Each task has a description, to help us finding the appropriate task.
Let's create our own Custom rake take by using rake generator:

$ rails g task my_rake

It will generate scaffold for our new rake task: >lib/tasks/my_rake.rake
open the file lib/tasks/my_rake.rake.It will look like this

namespace :my_rake do

end

Here we have not described any task.Now we will create a new rake with task 'hello'.

rails g task my_rake hello

Now open the file lib/tasks/my_rake.rake.It will look like this

namespace :my_rake do

  desc "TODO"
  task :hello => :environment do
  end

end

Here we have a task name hello. Now we can put our code here.

namespace :my_rake do

  desc "Say hello"
  task hello: :environment do
      puts "Hello World!"
  end

  desc "Say how are you"
  task :ask => :hello do
   puts "How are you?"
  end

  desc "Say hello to random user in our model"
  task hello_user: :environment do
      puts "Hello #{choose(User).name}"
  end

  desc "Select random user"
  task :all => [:hello,:hello_user,:ask]

  def choose(model_class)
    model_class.find(:first)
  end

end

Here I have four tasks. Let's call each one of them.

rake my_rake:hello
output // Hello World!

rake my_rake:ask
output // Hello World!
        How are you?

rake my_rake:hello_user
output // Hello John!
        
rake my_rake:all
output // Hello World!
         Hello John!
         How are you?