What is the difference between picking mountains and couplets?

In the center of the front wall of the main hall, there is often a framed word or painting with a relatively large size, which is called nave when viewed vertically. If the main hall is a painting, it can be accompanied by couplets on both sides, and the meanings are often related. This is a set of picking mountains.

As for the couplet, it's just a couplet!