This is the 374th most frequent Korean word.
보이고
"보이고" means "and [it] is visible" or "and [it] appears."
Here, '보이고' represents the fact that the stars can be seen, indicating visibility.
하늘에는 별이 반짝이며 보이고 있다.
In the sky, stars are twinkling and visible.
Here, '보이고' conveys the idea that his sincerity is becoming noticeable or clear.
그의 진심이 점점 더 보이고 있어요.
His sincerity is gradually becoming more apparent.
Here, '보이고' is used to express that the charm of the design is observable to the viewer.