そこで
So, and so ([someone] went and did…)machine translation
FormationAt the start of the following sentence: Sentence A。そこで、sentence B。
そこで connects a SITUATION with the ACTION someone deliberately took to deal with it: 部屋が暑かった。そこで、窓を開けた (the room was hot. So I opened the window). The implicit formula: "faced with situation A, I/they took the occasion to do B."
Two constraints: the second clause must be a deliberate ACTION (not a state or emotion), and it is usually something that already happened or a decision already settled. 暑かった。そこで、疲れた is wrong because "got tired" is not a deliberate action — in that case use それで.
Comparing within the family of causal conjunctions: それで states a natural result without stressing intent; だから is casual spoken "so"; したがって is formal and leans toward logical argument. そこで sits in between: polite enough for narrative writing, and always evoking the image of "seizing on that situation to go do something."
Examples
部屋が暑かったです。そこで、窓を開けました。
The room was hot. So I opened the window.
駅前に新しいパン屋ができました。そこで、さっそく買いに行ってみました。
A new bakery opened in front of the station. So I went right away to check it out.
アンケートで意見がたくさん集まりました。そこで、会社は新しい商品を作ることにしました。
The survey gathered a great many opinions. So the company decided to make a new product.