a resident foreigner: someone who has left his own land and people and settled long-term among Israel, living under its protection but without a native's land and family rights
A ger is a foreigner who has come to stay. He has left his homeland, often driven out by famine, war, or hardship, and put down roots in a community that is not his own. That makes him at once a permanent neighbor and a perpetual outsider: he lives in the land, keeps its customs, and may even share its worship, but he holds no ancestral land and stands outside the family and tribal networks that gave an Israelite his security.
That vulnerable in-between position is the heart of the word, and it pulls the term in three directions that are really one. Because the ger has no clan to defend him, the law sets him beside the widow and the orphan as a person the whole community must protect and provide for. Because Israel had itself been a body of foreigners in Egypt, the word becomes a name Israel gives itself, a reminder that its own footing in the land is a gift and not a right. And because the ger lives among the people of God, the law steadily folds him into Israel's worship and obligations, so that one rule governs the native and the foreigner alike.
The term should not be flattened into the modern idea of a tourist or an illegal migrant on the one hand, or a fully naturalized citizen on the other. The ger is a settled, recognized member of the community's life who still lacks the inheritance and kinship that would make him a native son.