门庭若市 The gate is like a market
Explanation
“门庭若市”这个成语原本是用来形容君主贤明，百姓对统治者都很拥护，经常到宫门前进谏，就像集市一样热闹，后来人们就用这个词来形容来的人很多，非常热闹的景象。
“Mén Tíng Ruò Shì” is an idiom that was originally used to describe a wise ruler, whose subjects were very supportive of him and often went to the palace gate to offer advice, making the palace gate as lively as a market. Later, the word was used to describe a place where there are many people coming and going, very lively.
Origin Story
战国时期，齐威王想成为一代明君，却发现臣子们都怕他，不敢进谏。于是，齐威王决定开放言路，鼓励臣子们大胆进言，并承诺有功者必有赏。消息传出，一时间，百姓争相进言，宫门前人山人海，热闹非凡，宛如集市一般。齐威王高兴极了，因为有了百姓们的建议，他能够更好地了解民情，治理国家，最终成为一代明君。
During the Warring States period, King Wei of Qi wanted to become a wise ruler, but he found that his ministers were afraid of him and dared not offer advice. So King Wei decided to open up the way for advice and encourage his ministers to boldly speak their minds, promising that those who deserved it would be rewarded. When the news got out, people rushed to the palace to offer advice. The palace gate was crowded, as lively as a market. King Wei was delighted, because with the advice of his people, he was able to better understand the people's needs, govern the country, and eventually become a wise ruler.
Usage
这个成语常用来形容人流如潮，场面热闹的景象，多用于商业、服务场所，也可以用于形容国家繁荣昌盛、百姓安居乐业的景象。
This idiom is often used to describe a scene where people are flowing in a stream, lively scene, mostly used in commercial and service places, but also can be used to describe the prosperous country and the people's peaceful life.
Examples
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这家店门庭若市，生意兴隆。
zhe jia dian men ting ruo shi, sheng yi xing long.
The store is crowded with customers, the business is booming.
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新开张的书店门庭若市，挤满了人。
xin kai zhang de shu dian men ting ruo shi, ji man le ren.
The newly opened bookstore is packed with people, it's a buzz.
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招聘会上门庭若市，求职者络绎不绝。
zhao pin hui shang men ting ruo shi, qiu zhi zhe luo yi bu jue.
The job fair is crowded with job seekers, people are coming and going.