Answer:
The correct answer to the question: What is the following key word used for: actually, would be: as an explanation or illustration.
Step-by-step explanation:
The reason for this being the correct choice as to what is meant when the word "actually" is used in a sentence, is that the word itself is defined as a keyword that indicates an intention to find out the truth of something that happened, clarifying that there is something more to be found, to be explained, or to be shown, or illustrated. It is also defined as word used to suggest something, or invite to suggest something that was not expected. It opens up a person to understand that whatever comes after this word, will be a further explanation, or illustration of that which was not known before, or was not comprehended before.