Pronoun first, noun later
In dislocación a la derecha (right dislocation) the topic sits at the end. The sentence already contains the matching pronoun, and the noun is tagged on afterwards. Casual English does the same: It's lovely, that cake.
Neutral
No conozco a esa chica.
I don't know that girl.
A plain statement.
Topic at the end
No la conozco, a esa chica.
I don't know her, that girl.
The weight is on No la conozco; who is meant is already clear.
The pattern
What the afterthought is for
Right dislocation is typical of conversation. It puts the comment up front and supplies the topic afterwards: to make clear what you mean, because it is in the air anyway, or as a confirming echo.
Making it clear
¿Lo has firmado ya, el contrato?
Have you signed it yet, the contract?
The afterthought confirms what lo refers to.
Se lo dije ayer, a tu jefe.
I told him yesterday, your boss.
Indirect object, with a.
Judging and confirming
Está buenísima, esta tortilla.
It's really good, this tortilla.
The subject can come last too; it needs no pronoun.
Ya lo sé, que estás cansado.
I know, that you're tired.
A whole clause as afterthought, announced by lo.
Left or right?
Both positions use the same pronoun, but they place the weight differently. On the left, the topic opens the sentence, which also works in writing. On the right, the sentence belongs to the comment and the topic trails in afterwards. In reports and emails this sounds too casual.
Left, topic opens
Las entradas, las compré ayer.
The tickets, I bought them yesterday.
Right, topic trails
Las compré ayer, las entradas.
I bought them yesterday, the tickets.
