What does Hemingway's "Iceberg" analogy mean?

What does Hemingway's "Iceberg" analogy mean?

Typical of this“iceberg" analogy is Hemingway's style.He thinks good literary writing should be able to make readers feel the emotion of the characters directly and the best way to produce the effect is to set down exactly every particular feeling without any authorial comments, without emotive language,and with a bare minimum of adjectives and adverbs.