We use "swój" to talk about the possession of the subject in the sentence. For example: * (Ty) Sprzedałaś swój dom - You sold your house ("You" is the subject of the sentence and the house belonged to "you", therefore we use "swój" instead of "twój") * Maria zgubiła swoją torebkę - Maria lost her purse (Maria is the subject of the sentence, the purse was hers, so it's "swój" again) On the other hand, we use "twój" (or "mój/jego/jej/nasz/wasz/ich) when the subject of the sentence is not "ty" (or "ja/on/ona/my/wy/oni/one"). For example: *Anna pożyczyła twojego laptopa - Anna borrowed your laptop (Here, the subject of the sentence is Anna, but the laptop belongs to you, so we use "twój") *(Ja) Widziałam twój samochód - I saw your car ("I" is the subject, but car belongs to you, so it's "twój") In Polish it is acceptable to use "mój", "twój", "nasz" i "wasz" instead of "swój" (don't do it for 3rd person singular and plural because that can be confusing). That means sentence: *(Ty) Sprzedałaś swój dom. Can also be said as: *(Ty) Sprzedałaś twój dom. I hope that you will find it helpful :)