Final answer:
The phrase "All the world is a stage" is an example of a metaphor, which is a direct comparison between two unlike things without using 'like' or 'as'.
Step-by-step explanation:
The phrase "All the world is a stage" is an example of a metaphor. A metaphor is a figure of speech that directly compares two unlike things without using the words 'like' or 'as'. Unlike a simile which compares two things using 'like' or 'as' (e.g., "My love is like a red, red rose" - Robert Burns), a metaphor makes the comparison by stating one thing is another (e.g., "Time is a thief").
The phrase in question does not use 'like' or 'as' and instead directly states that the world is a stage, thus speaking metaphorically by equating the world with a place where everyone plays their part as if they were characters in a play. This line originates from William Shakespeare's play, 'As You Like It', and it encapsulates the essence of life as a performance.