app_tables is a software library.
app_tables.questions is a table.
app_tables.questions.search is a function that returns a (kinda) list of rows.
rows = app_tables.questions.search() executes the function (because of the parentheses) and assigns the (kinda) list of rows to the variable rows.
rows[0] returns the first row in the list.
row = rows[0] assigns the first row of rows to the variable row.
row['column_name'] returns the value of the column column_name of row.
You can do all in a less readable one liner: app_tables.questions.search()[0]['column_name'].
You don’t use the property items for the TextArea. You assign it to its text property. Something like:
rows = app_tables.questions.search()
value = rows[0]['column_name']
self.text_area_1.text = value