Es la primera mitad de un verbo infinitivo transitivo que es sobreentiendo en el contexto de la conversación. En ingles, cada verbo infinitivo empieza con "to".
A: Do you want to go to the movies?
B: I'd love to [go to the movies].
A: Who wants to try some cake?
B: I want to [try it].
A: When you were little, did you want to become an astronaut?
B: Yes, I wanted to [become that].
A: Don't you need to go to school today?
B: No, I don't have to [go there].