Refers to a place relatively near the listener. Contrasts with ここ (near speaker) and あそこ (far from both).
そこに座ってもいいですか。
May I sit there (near you)?
there (place just mentioned); that place
Refers to a place that was just mentioned in conversation or text.
I went to the park yesterday. That place was very quiet.
Refers to a point in a conversation or story just raised; often used to comment on or continue from that point.
That's the problem.
Archaic pronoun for 'you', no longer used in modern Japanese.
In classical Japanese, そこ can mean 'you'.
そこ is a demonstrative meaning 'there', while どこ is the interrogative 'where', and learners sometimes mix up the ko-so-a-do forms.