Meg is similar to pedig. Both of them, if they connect two clauses like the ones above, come after the subject of the second clause.

If you used és in this sentence, it would be just two simple statements. These are the tables; those are the chairs. With meg or pedig, you express a contrast between these two statements. But I think that's shown well by the conjunction while in the preferred translation.

Be careful: while using meg and pedig would be synonymous in this sentence, if you put pedig before the subject ("Ezek az asztalok, pedig azok a székek"), the meaning changes: "These are the tables, even though those are the chairs".