How do I "initiate" dataset.setfilter.eq

Hello, I want to ask this question in general terms. I don’t want to bother people with reading the exact code.
I know I can do something like

import wixdata

then
$w(#dataset).setfilter(
.eq (some field, some criteria
)
Late I use something like this
$w(#dataset).getCurrentitme()._someField

But it only refers to ONLY THE FIRST RECORD! not the one that matches some field = some criteria.

Why is that? am I missing something? how do I “initiate” the filter and make sure the “current item” is the first item and meet the criteria?

I followed the discussion boards and I think I can use the right syntax. I want to ask the CONCEPTUAL question.

By the way, I think Wix is doing a great job! I appreciate the support.

GetCurrentItem exists only for dynamic dataset. Current item works only on dynamic datasets.

The other one is for the normal Dataset.