This is the 618th most frequent Italian word.
sulla
"Sulla" means "on the" or "about the" (feminine singular).
Here, 'sulla' is a contraction of 'su' (on) and 'la' (the), indicating location on a specific feminine singular noun, 'tavola' (table).
La tazza è sulla tavola.
The cup is on the table.
In this example, 'sulla' combines 'su' (on/about) with 'la' (the) to introduce a topic, in this case, 'storia dell'arte' (history of art).
Ho letto un articolo sulla storia dell'arte.
I read an article about the history of art.
Here, 'sulla' again combines 'su' (on) and 'la' (the) to denote a physical movement or effect happening in contact with 'finestra' (window).