1Refers to a place near the listener but away from the speaker. Used to point to a spot close to the person you're talking to, as in そこに置いて 'put it there'.
その本、読み終わったらそこに置いておいてね。
Once you finish reading that book, just leave it there (by you).
そこ、危ないから立たないで。
It's dangerous there — please don't stand there.
すみません、そこにあるペンを取ってもらえますか。
Excuse me, could you hand me the pen over there by you?
鍵はそこの引き出しの中にあります。
The key is in that drawer near you.
2Refers to a place that was just mentioned in the conversation; means 'that place'.
先週行ったラーメン屋、そこ、また行きたいな。
That ramen shop we went to last week — I want to go back there.
田舎に小さな喫茶店があって、そこでよく本を読んだ。
There was a small café in the countryside, and I often read books there.
資料は会議室の棚にある。そこを確認してもらえる？
The documents are on the shelf in the meeting room. Can you check there?
3Refers to a point or matter just mentioned in the discussion; used to mean 'that point' or 'that aspect'.
給料が下がった。そこが一番の不満点だ。
Our pay was cut. That's the biggest source of complaint.
彼はよく遅刻する。そこを直さないと信用を失うよ。
He's often late. If he doesn't fix that, he'll lose people's trust.
4(Archaic) An old usage where そこ functioned as a second-person pronoun meaning 'you'. Essentially unused in modern Japanese, surviving only in classical texts or period-drama dialogue.