When I click the Installation Details in eclipse,
I got this tab for Installed software
and a tab for Features
and a tab for plug-ins.
What are the relationships between eclipse software, eclipse features, and eclipse plugin as is shown in this window?
I guess Help -> Install New Software ... to install software, and software is comprised of a bunch of related plugins. Those two tabs are just the same contents (software names/plugin names) that is installed from Install New Software ... menu?
In his answer https://stackoverflow.com/a/12863077/260127, Bananeweizen says Eclipse "features" are the smallest installable pieces of Eclipse applications for users (e.g. the Java development toolkit). They consist of multiple plugins, where plugins are the smallest pieces that make sense from the developers point of view (e.g. org.eclipse.jdt.core, org.eclipse.jdt.ui, org.eclipse.jdt.somethingelse)., but to me it seems like eclipse feature is almost the same as eclipse software, and eclipse application is a set of eclipse software(feature) on top of eclipse platform.
“Installed software” is that subset of features, which you as a user actively choose to install in this Eclipse instance.
The features list on the other hand contains all features installed in this Eclipse instance. It includes all items from “installed software” and it contains the dependencies of the items from “installed software”. Those are the features which you did not choose to install by yourself, but the Eclipse P2 update manager decided that, to be able to satisfy your installation request.
So again, an Eclipse installation process installs features, some of them on request of the user, some of them on request of the system to be able to install those from the user.
To make this all more complicated, Eclipse features are often referred to as “plugins” by Eclipse users, although that is not correct. So if you read about something like “installing the PHP plugin”, that really refers to installing the PHP feature, which again consists of multiple plugins (but you don’t see those as an Eclipse user, only as an Eclipse developer).
You can double click one of the features in that dialog to see the list of plugins it contains.