For example, the following is a brief extract from my novel The Captain and The Countess, in which Edward, Captain Howard sees the Countess for the first time.
“Lady Sinclair,” someone murmured.
Edward turned. He gazed without blinking at the acclaimed beauty, whose sobriquet was ‘The Fatal Widow’.
The countess remained in the doorway, her cool blue eyes speculative.
Edward whistled low. Could her shocking reputation be no more than tittle-tattle? His artist’s eyes observed her. Rumour did not lie about her Saxon beauty.
The reader sees Edward's reaction to the countess and his reaction to her beauty.
Instead of 'head-hopping' - switching from one person to another person's viewpoint - sticking to a single viewpoint makes it clear to the reader which character they should identify with.
Of course, if a short story or novel is written in the first person the entire story is from a single viewpoint.