Bottom line: there are green trees by the pool, red rain under the trees, and rain falls to the west.
Analysis: first, observe the number of words in couplets. The number of words in the upper and lower couplets should be consistent, rhyming and even.
Extended data
The characteristics of couplets are mainly manifested in structure and language. Couplets can be called "dual structure" style. Standard couplets always consist of two opposing parts. The former part is called "Lian", which is also called "sentence", "antithesis" and "antithesis". The latter part is called "bottom link", which is also called "antithesis", "antithesis" and "antithesis".
These two parts are paired. Only the upper part or the lower part can be regarded as semi-joint. Of course, many couplets, especially those written and hung, have horizontal comments in addition to the upper and lower couplets.
Horizontal criticism is an organic part of this kind of couplets, which is often a summary, the finishing touch or compatible with couplets. Generally, it is four words, but also two, three, five and seven words.