This question refers to Book 18 of Homer's Odyssey. In this book, Odysseus has returned from the Trojan War after being away from his native land of Ithaca for 20 years. When he returns to his home, he finds that it is infested with men who are trying to marry his wife Penelope. Rather than charge directly into this hostile environment, Odysseus tries to investigate the situation first. Thus, he basically sneaks back into his own home. Goddess Athena has disguised him as a beggar.
So, when Odysseus enters his palace, he looks like a ragged beggar. Odysseus discovers, however, that he is not the only beggar in the palace. Another beggar, named Irus (also spelled Iros; not to be confused with Iris, goddess of the rainbow), has already been making the rounds of Penelope's suitors for some time. Therefore, Irus sees this new beggar as a threat to his "territory." Accordingly, Irus the beggar wants to drive Odysseus the beggar away from the palace. Irus wants any handouts to come to him rather than Odysseus.
Eventually, the two beggars fight and Odysseus pounds Irus and drags him out of the palace.