The particle "と" in Japanese is primarily used to indicate a connection or relationship between two nouns. It can mean "and" when listing items, such as in the phrase "りんごとバナナ" (apple and banana). Additionally, "と" can express a quote or direct speech, as in "彼は「行く」と言った" (He said, "I will go"). Another important use of "と" is to indicate a condition or a comparison. For example, in the sentence "雨が降ると、外に出ない" (If it rains, I won't go outside), "と" shows the condition under which the action occurs. This versatility makes "と" a fundamental particle in Japanese grammar.