It is the diminutive of “plaza”. Plaza is a public square. Placita is either a small plaza or a cute or friendly way of referring to one. Usually kids use a lot of diminutives. Also, adults use them to sound nicer, friendlier or just because you are trying to “soften the word” (assuming this is a normal-sized plaza). But you can also call a plaza as a placita if you think it is small.

Yes, you are correct