This is the 154th most frequent Italian word.
qualcosa
"Something."
'Qualcosa' here metaphorically references an intuition or feeling, used as a subject in the sentence.
Qualcosa mi dice che dovrebbe piovere presto.
Something tells me that it should rain soon.
Here, 'qualcosa' means 'something' and refers to an indefinite subject which is elaborated as 'di interessante'.
Ho visto qualcosa di interessante al mercato.
I saw something interesting at the market.
In this context, 'qualcosa' represents an unspecified item of food or drink to consume.