What is the client_email, developer_token, useragent and application_token in adword api?

Hi, I try learn more about google API and I get the code you see in code snippet for I made a test and closer to the tool.
I have doubts about this part of the code:
 $email = 'INSERT_LOGIN_EMAIL_HERE';
 $password = 'INSERT_PASSWORD_HERE';
 $client_email = 'INSERT_CLIENT_LOGIN_EMAIL_HERE';
 $useragent = 'INSERT_COMPANY_NAME: AdWords API PHP Sample Code';
 $developer_token = 'INSERT_DEVELOPER_TOKEN_HERE';
 $application_token = 'INSERT_APPLICATION_TOKEN_HERE';

I have account in google adwords. So email and password can be the same I use for login in my adwords account, right?
The client_email is the same of my e-mail?
How I get useragent, developer_token and application_token.

Regards, JC

<?php
 // Copyright 2008, Google Inc. All Rights Reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 // http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 /** This code sample retrieves variations for a seed keyword. */
 
 require_once('soapclientfactory.php');
 
 # Provide AdWords login information.
 $email = 'INSERT_LOGIN_EMAIL_HERE';
 $password = 'INSERT_PASSWORD_HERE';
 $client_email = 'INSERT_CLIENT_LOGIN_EMAIL_HERE';
 $useragent = 'INSERT_COMPANY_NAME: AdWords API PHP Sample Code';
 $developer_token = 'INSERT_DEVELOPER_TOKEN_HERE';
 $application_token = 'INSERT_APPLICATION_TOKEN_HERE';
 
 # Define SOAP headers.
 $headers =
 '<email>' . $email . '</email>'.
 '<password>' . $password . '</password>' .
 '<clientEmail>' . $client_email . '</clientEmail>' .
 '<useragent>' . $useragent . '</useragent>' .
 '<developerToken>' . $developer_token . '</developerToken>' .
 '<applicationToken>' . $application_token . '</applicationToken>';
 
 # Set up service connection. To view XML request/response, change value of
 # $debug to 1. To send requests to production environment, replace
 # "sandbox.google.com" with "adwords.google.com".
 $namespace = 'https://sandbox.google.com/api/adwords/v12';
 $keyword_tool_service = SoapClientFactory::GetClient(
 $namespace . '/KeywordToolService?wsdl', 'wsdl');
 $keyword_tool_service->setHeaders($headers);
 $debug = 0;
 
 # Create seed keyword structure.
 $seed_keyword =
 '<negative>false</negative>' .
 '<text>mars cruise</text>' .
 '<type>Broad</type>';
 $use_synonyms = '<useSynonyms>true</useSynonyms>';
 
 # Get keyword variations.
 $request_xml =
 '<getKeywordVariations>' .
 '<seedKeywords>' . $seed_keyword . '</seedKeywords>' .
 $use_synonyms .
 '<languages>en</languages>' .
 '<countries>US</countries>' .
 '</getKeywordVariations>';
 $variation_lists =
 $keyword_tool_service->call('getKeywordVariations', $request_xml);
 $variation_lists = $variation_lists['getKeywordVariationsReturn'];
 if ($debug) show_xml($keyword_tool_service);
 if ($keyword_tool_service->fault) show_fault($keyword_tool_service);
 
 # Display keyword variations.
 $to_consider = $variation_lists['additionalToConsider'];
 echo 'List of additional keywords to consider has ' . count($to_consider) .
 ' variation(s).' . "\n";
 
 $more_specific = $variation_lists['moreSpecific'];
 echo 'List of popular queries with given seed has ' . count($more_specific) .
 ' variation(s).' . "\n";
 
 function show_xml($service) {
 echo $service->request;
 echo $service->response;
 echo "\n";
 }
 
 function show_fault($service) {
 echo "\n";
 echo 'Fault: ' . $service->fault . "\n";
 echo 'Code: ' . $service->faultcode . "\n";
 echo 'String: ' . $service->faultstring . "\n";
 echo 'Detail: ' . $service->faultdetail . "\n";
 exit(0);
 }
 ?>

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