This is the 9249th most frequent Polish word.
tomek
"Tomek" is a Polish male given name, equivalent to "Tom" or "Thomas" in English.
Here, 'Tomek' is a proper noun, specifically a male given name, used as the subject of the sentence.
Tomek idzie do szkoły.
Tomek is going to school.
'Tomek' is used here in locative case, referring to the individual (male name Tomek) the book is about.
Mam książkę o Tomku.
I have a book about Tomek.
In this sentence, 'Tomek' is the nominative subject performing the action of buying the car.