Eclipse Add to build path option

I am using eclipse. I was told that, whenever I import a package for new functionality, I should to add it to lib folder and then right-click on it -> Build Path -> Add to build path.
What happens if I just import the package into my lib folder and leave it alone?
I don't understand whats going on behind the scenes. Why am I required to do that?
Thanks in advance.

Haritha Gorijavolu wrote: . . . What happens if I just import the package into my lib folder and leave it alone? . . .

don't know. Have you tried it?

Because Eclipse doesn't treat the "lib" folder as any special folder, so it doesn't know the files in it should be added to the class path / build path. You must specify this specifically for each single JAR file you need.

Moving to our IDEs forum.

got it. Thanks!

A little off the topic, but hopefully helpful: use Maven for your builds and use the m2eclipse plugin. Then the dependencies in your Maven build script (pom.xml) will be synched with the libraries that Eclipse knows about.