What are validators in eclipse IDE?

In order to speed up the eclipse, we can disable one or more validators in Eclipse IDE. It actually speeds up the loading of eclipse.

My question is not how to disable those validators. I know how to do that.

My question is What do those validators do? Why do we need them? What is the danger of disabling those validators? If we do not want them, why does eclipse comes with them?

If we use a build tool like ant to build our project, does disabling those validators still have any effect?

Quoting the offcial docs for juno

The validators used depend on the global and project validation settings. When you validate a project manually, the global settings are used unless both of the following are true:

• The Allow projects to override these preference settings check box is selected on the global validation preferences page.

• The Override validation preferences check box is selected on the project's validation preferences page.

What does that actually mean?