What is the difference between easy and easily as both playing role of an adverb?

You're right to notice the similarity and confusion between "easy" and "easily"! They both function as adverbs, but they describe different things:

Easy describes how something is done:

* "The test was easy." This means the test itself was simple.

* "He made it look easy." This means the act of doing it appeared simple.

Easily describes how well something is done:

* "She answered the question easily." This means she had no trouble answering the question.

* "He can easily lift that weight." This means he can lift the weight with little effort.

In short:

* Easy modifies the noun (or adjective) describing the thing being done.

* Easily modifies the verb, describing how the action is performed.

Here's a simple way to remember the difference:

* Easy = The task itself is simple.

* Easily = The person doing the task has no trouble with it.