Cá means here (aqui). It’s used in several very common phrases and you can’t simply substitute it for aqui.
It’s most often used with para or de.
Para cá evolved from venha para aqui. If you say it fast enough you’ll see that it’s just a natural shorthand to say cá rather than aqui.
venha para aqui » venha para cá » vam para cá » vem cá!
These translate as Come over here! as well as Listen here!
It’s usually used as a command, so the tu form of the imperative of VIR is commonly used: vem. it just sounds better 😉
Mãe vem para cá! Vem pro Rio de Janeiro. Come over here! Come to RJ.
Vem cá! Você sabe que eu estou deixando você ganhar, não é? Liten here! You know that I'm letting you win, right?
Eu passei para cá correndo. I came over here in a hurry.
de cá para lá from here to there
do lado de cá from this side here