This is the 6729th most frequent Polish word.
egipt
Egypt.
Here, 'Egipt' is used as a proper noun referring to the country named Egypt.
Egipt jest popularnym celem podróży dla turystów.
Egypt is a popular travel destination for tourists.
In this sentence, 'Egiptu' is the genitive case of 'Egipt', used to show possession or association with history.
Mój przyjaciel studiował historię Egiptu starożytnego.
My friend studied the history of ancient Egypt.
In this sentence, 'Egipt' is used in its basic nominative form as the object of the action 'visit' (though not marked by a case change in English).