Hi,
Refer Liferay Documentation to get more idea.
https://www.liferay.com/documentation/liferay-portal/6.2/development/-/ai/advanced-customization-with-ext-plugins-liferay-portal-6-2-dev-guide-12-en
https://www.liferay.com/documentation/liferay-portal/6.0/development/-/ai/ext-plugins
HTH!