Ich lege das Buch auf den Tisch.
English: I put the book onto the table.
Wechselpräpositionen are German prepositions that can take either the accusative or dative case, depending on whether there is movement (change of place) or not.
Use these prepositions in German to describe where something is (position - dative) or where something is going (direction/movement - accusative).
Ich lege das Buch auf den Tisch.
English: I put the book onto the table.
Das Buch liegt auf dem Tisch.
English: The book is lying on the table.
Wir gehen in die Schule.
English: We are going into the school.
Wir sind in der Schule.
English: We are in the school.
Die Katze schläft unter dem Bett.
English: The cat is sleeping under the bed.