PHP include and require differences

Just contacted PHP soon, encountered include and require, in the online search for a long time, a lot of people have done a comparison, some are not correct, misleading, the most authoritative right answer here: http://cn.php.net/manual/zh/function.include.php.
Look, if I don't understand, I've done the following tests,
Situation One:
<?php
Include ("./est.php"); Est.php does not exist
echo "<br>continue ...";
?>

Test results:
Warning:include (./est.php): Failed to open stream:no such file or directory in .../test1.php on line 2 warning:include ( ): Failed opening './est.php ' for inclusion (include_path= '.:/ Usr/local/cellar/php/5.3.10/lib/php ') in .../test1.php on line 2
Continue ...

Situation Two:
<?php
Require ("./est.php");
echo "<br>continue ...";
?>

Test results:
Warning:require (./est.php): Failed to open stream:no such file or directory in .../test1.php on line 2 Fatal error:requ IRE (): Failed opening required './est.php ' (include_path= '.:/ Usr/local/cellar/php/5.3.10/lib/php ') in .../test1.php on line 2
Here the continue string is not printed.

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