'this' is used in Java and Quest, and 'self' is used in Python (Python also requires that you put the 'self' as the first parameter for a function, it doesn't do it behind the scenes for you).
example of 'this' used in quest:
<type name="character">
<attr name="display_alias_and_strength" type="script">
msg(this.alias + " Strength: " + this.strength)
</attr>
</type>
<object name="player">
<inherit name="character" />
<attr name="alias" type="string">HK</attr>
<attr name="strength" type="int">100</attr>
</object>
<object name="orc_1">
<inherit name="character" />
<attr name="alias" type="string">orc</attr>
<attr name="strength" type="int">25</attr>
</object>