Wat
“Wat” asks what something is. In the dialogue it stands at the beginning of “Wat is dit?” and “Wat is dat?”, before “is”. In a new example, you can use “Wat is je naam?” when asking someone’s name.
is
“is” connects a thing or person with information about it. In the dialogue, it is used in questions such as “Wat is dit?” and in statements such as “Deze is van mij.” Its position depends on the sentence: it follows the question word in these questions and comes after the pointing word in these statements.
dit
“dit” means “this” for the thing being pointed to in “Wat is dit?”. It refers to something near or currently indicated by the speaker. Use it when asking about a nearby or selected thing; in a new example, “Dit is mijn boek” identifies a nearby item.
dat
“dat” means “that” in “Wat is dat?” and “Wie is dat?”. It points to something or someone being indicated as separate from the speaker. Use it when asking about a person or thing over there; in a new example, “Dat is mijn tas” identifies a more distant item.
Wie
“Wie” asks who a person is. In “Wie is dat?”, it appears at the beginning of the question before “is” and “dat”. Use it when identifying someone you are pointing to or referring to; in a new example, “Wie is zij?” asks who a woman is.
Welke
“Welke” asks which one is intended or belongs to someone. In “Welke is van jou?”, it begins the question and is followed by “is van jou”. Use it when choosing one item from several possibilities, such as when asking which bag belongs to the other person.
van
“van” helps express belonging in the exact phrases “van jou” and “van mij”. The ownership meaning comes from the whole phrase: “van jou” means belonging to you, while “van mij” means belonging to me. In the reusable pattern [item] is van [person], the person who owns the item comes after “van”.
jou
“jou” identifies the person being addressed as the owner in “van jou”. The phrase “van jou” means that something belongs to you. Use “jou” after “van” when asking or stating whether an item belongs to the person you are speaking to; in a new example, “Is dit van jou?” asks whether it is theirs.
Deze
“Deze” means “this one” in “Deze is van mij.” It refers to the item currently selected or pointed out and comes before “is”. Use it when choosing a nearby item and stating who owns it; in a new example, “Deze is voor jou” identifies this particular item as intended for the other person.
mij
“mij” identifies the speaker as the owner in “van mij”. The whole phrase “van mij” means belonging to me. Use “mij” after “van” when stating that an item is yours; in a new example, “Dat is van mij” says that the indicated item belongs to the speaker.
Die
“Die” means “that one” in “Die is van jou.” It points to the selected item and comes before “is”. Use it when referring to a particular item that is farther away or already being indicated; in a new example, “Die is mijn jas” identifies that item.