Following are the steps to create an example module:

[t@cookbook ~]$ puppet module generate thomas-memcached

Puppet uses Semantic Versioning (semver.org) to version modules.What version is this module? [0.1.0]-->Who wrote this module? [thomas]-->What license does this module code fall under? [Apache-2.0]-->How would you describe this module in a single sentence?--> A module to install memcachedWhere is this module's source code repository?--> github.com/uphillian/thomas-memcachedWhere can others go to learn more about this module? [https://github.com/uphillian/thomas-memcached]-->Where can others go to file issues about this module? [https://github.com/uphillian/thomas-memcached/issues]-->{"name": "thomas-memcached","version": "0.1.0","author": "thomas","summary": "A module to install memcached","license": "Apache-2.0","source": "github.com/uphillian/thomas-memcached","project_page": "https://github.com/uphillian/thomasmemcached","issues_url": "https://github.com/uphillian/thomas-memcached/issues","dependencies": [{"name": "puppetlabs-stdlib","version_requirement": ">= 1.0.0"}]"data_provider": null}----------------------------------------About to generate this metadata; continue? [n/Y]--> yNotice: Generating module at /home/vagrant/memcached...Notice: Populating templates...Finished; module generated in memcached.memcached/specmemcached/spec/spec_helper.rbmemcached/spec/classesmemcached/spec/classes/init_spec.rbmemcached/metadata.jsonmemcached/manifestsmemcached/manifests/init.ppmemcached/Gemfilememcached/examplesmemcached/examples/init.ppmemcached/README.mdmemcached/Rakefile

This command creates the module directory and creates some empty files as starting points.

class memcached {
  package { 'memcached': ensure => installed, }
  file { '/etc/memcached.conf':
    source  => 'puppet:///modules/memcached/memcached.conf',
    owner   => 'root',
    group   => 'root',
    mode    => '0644',
    require => Package['memcached'],
 }
 service { 'memcached':
   ensure  => running,
   enable  => true,
   require => [Package['memcached'],
               File['/etc/memcached.conf']],
 }
}

[t@cookbook memcached]$ mkdir files
[t@cookbook memcached]$ echo "-m 64 -p 11211 -u nobody -l 127.0.0.1" > files/memcached.conf

t@cookbook:memcached$ sudo /opt/puppetlabs/bin/puppet apply --modulepath=/home/vagrant -e 'include memcached'Warning: ModuleLoader: module 'memcached' has unresolved dependencies - it will only see those that are resolved. Use 'puppet module list --tree' to see information about modules  (file & line not available)Notice: Compiled catalog for cookbook.strangled.net in environment production in 0.46 secondsNotice: /Stage[main]/Memcached/Package[memcached]/ensure: createdNotice: /Stage[main]/Memcached/File[/etc/memcached.conf]/ensure: defined content as '{md5}febccf4a987759cf4f1558cc625fbea9'Notice: /Stage[main]/Memcached/Service[memcached]/ensure: ensure changed 'stopped' to 'running'Notice: Applied catalog in 6.99 seconds

t@cookbook:memcached$ sudo /opt/puppetlabs/bin/puppet resource service memcached
service { 'memcached':
 ensure => 'running',
 enable => 'true',
}
t@cookbook:memcached$ sudo systemctl status memcached
memcached.service - Memcached
  Loaded: loaded (/usr/lib/systemd/system/memcached.service; enabled; vendor preset: disabled)
  Active: active (running) since Thu 2017-12-28 05:17:41 UTC; 3min 28s ago
Main PID: 4057 (memcached)
  CGroup: /system.slice/memcached.service
          └─4057 /usr/bin/memcached -u memcached -p 11211 -m 64 -c 1024

Dec 28 05:17:41 cookbook systemd[1]: Started Memcached.
Dec 28 05:17:41 cookbook systemd[1]: Starting Memcached...
Note that /opt/puppetlabs/bin/puppet may not be in root's path, use the full path or add the path to a file in /etc/profile.d. 

When we created the module using Puppet's module generate command, we used the name thomas-memcached. The name before the hyphen is your username or your username on Puppet forge (an online repository of modules). Modules have a specific directory structure. Not all of these directories need to be present, but if they are, this is how they should be organized:

modules/
└MODULE_NAME/ never use a dash (-) in a module name
└examples/ example usage of the module
└files/ flat files used by the module
└lib/
  └facter/ define new facts for facter
  └puppet/
    └parser/
      └functions/ define a new puppet function, like sort()
    └provider/ define a provider for a new or existing type
    └util/ define helper functions (in ruby)
    └type/ define a new type in puppet
└manifests/
└init.pp class MODULE_NAME { }
└spec/ rSpec tests
└templates/ EPP or ERB template files used by the module

All manifest files (those containing Puppet code) live in the manifests directory. In our example, the memcached class is defined in the manifests/init.pp file, which will be imported automatically.

Inside the memcached class, we refer to the memcached.conf file:

file { '/etc/memcached.conf':
  source => 'puppet:///modules/memcached/memcached.conf',
}

The preceding source parameter tells Puppet to look for the file in:

MODULEPATH/ (/home/vagrant/)
 └memcached/
   └files/
     └memcached.conf

Learn to love modules because they'll make your Puppet life a lot easier. They're not complicated, however; practice and experience will help you judge when things should be grouped into modules, and how best to arrange your module structure. Modules can hold more than manifests and files, as we'll see in the next two sections.

file { '/etc/memcached.conf':
  content => epp('memcached/memcached.conf.epp),
}

MODULEPATH/memcached/templates/memcached.conf.epp