Format Source Resource File
Android Strings     res/values/strings.xml
iOS/Mac Strings Localizable.strings, InfoPList.strings
Java Properties *.properties
RESW *.resw
RESX *.resx
XLIFF *.xlf, *.xliff, *.sdlxliff, *.mxliff
PO File *.pot

Android Strings Example

Source Resource File (English): res/values/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello" description="Greeting from Main UI">Hello!</string>
</resources>

Localized Resource File (Spanish): res/values-es/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello" description="Greeting from Main UI">¡Hola!</string>
</resources>

iOS/Mac Strings Example

Source Resource File (English): en.lproj/Localizable.strings

/* Greeting from Main UI */
"Hello!" = "Hello!";

Localized Resource File (Spanish): es.lproj/Localizable.strings

/* Greeting from Main UI */
"Hello!" = "¡Hola!";

Java Properties Example

Source Resource File (English): en.properties

# Greeting from Main UI
hello = Hello!

Localized Resource File (Spanish): es.properties

# Greeting from Main UI
hello = ¡Hola!

RESW Example

Source Resource File (English): en/Resources.resw

<?xml version="1.0" encoding="utf-8"?>
<root>
  <data name="hello" xml:space="preserve">
    <value>Hello!</value>
    <comment>Greeting from Main UI</comment>
  </data>
</root>

Localized Resource File (Spanish): es/Resources.resw

<?xml version="1.0" encoding="utf-8"?>
<root>
  <data name="hello" xml:space="preserve">
    <value>¡Hola!</value>
    <comment>Greeting from Main UI</comment>
  </data>
</root>

RESX Example

Source Resource File (English): Resources.resx

<?xml version="1.0" encoding="utf-8"?>
<root>
  <data name="hello" xml:space="preserve">
    <value>Hello!</value>
    <comment>Greeting from Main UI</comment>
  </data>
</root>

Localized Resource File (Spanish): Resources.es-ES.resx

<?xml version="1.0" encoding="utf-8"?>
<root>
  <data name="hello" xml:space="preserve">
    <value>¡Hola!</value>
    <comment>Greeting from Main UI</comment>
  </data>
</root>

XLIFF Example

Source Resource File (English): resource.xliff

<?xml version="1.0" encoding="UTF-8"?>
<xliff xmlns="urn:oasis:names:tc:xliff:document:2.0" version="2.0">
  <file original="" source-language="en" datatype="x-undefined">
    <body>
      <trans-unit id="1" resname="hello" datatype="php">
        <source>Hello!</source>
        <note>Greeting from Main UI</note>
      </trans-unit>
    </body>
  </file>
</xliff>   

Localized Resource File (Spanish): resource_es-ES.xliff

<?xml version="1.0" encoding="UTF-8"?>
<xliff xmlns="urn:oasis:names:tc:xliff:document:2.0" version="2.0">
  <file original="" source-language="en" datatype="x-undefined" target-language="es-es">
    <body>
      <trans-unit id="1" resname="hello" datatype="php">
        <source>Hello!</source>
        <target xml:lang="es-es">¡Hola!</target>
        <note>Greeting from Main UI</note>
      </trans-unit>
    </body>
  </file>
</xliff>   

PO File Example

Source Resource File (English): messages.pot

msgid ""
msgstr ""
"Project-Id-Version: PACKAGE VERSION\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2017-02-24 11:50-0800\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <LL@li.org>\n"
"Language: \n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=utf-8\n"
"Content-Transfer-Encoding: 8bit\n"

#. Greeting from Main UI
#: file.js:2
msgctxt "hello"
msgid "Hello!"
msgstr ""

Localized Resource File (Spanish): es_ES/LC_MESSAGES/messages.po

msgid ""
msgstr ""
"Project-Id-Version: PACKAGE VERSION\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2017-02-24 11:50-0800\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <LL@li.org>\n"
"Language: \n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=utf-8\n"
"Content-Transfer-Encoding: 8bit\n"

#. Greeting from Main UI
#: file.js:2
msgctxt "hello"
msgid "Hello!"
msgstr "¡Hola!"