Word order in questions differs from word order in declarative clauses. As illustrated in the examples below, questions
(a) are introduced by an interrogative pronoun (wh-element);
(b) exhibit subject auxiliary inversion.

Declarative: Anne will buy a new car.
Question: What will Anne buy?

In generative approaches to syntax it is assumed that questions are derived from their declarative counterparts by moving constituents to positions inside the CP. There are two types of movement:
(a) INFL-to-COMP movement: the element that is located in INFL in declarative clauses moves to COMP (i.e. the modal, periphrastic do or have / be).
(b) WH-movement: the interrogative pronoun (e.g. what in the example above) moves out of its base-generated position (in our example the complement to V) to the specifier position of CP.
Moved constituents leave a trace (t) in the position they leave. By convention the moved constituent and the trace are co-indexed (i.e. they have the same index).

Example: INFL-to-COMP and WH-movement
What will Anne buy?

INFL-to-COMP movement

Exercises on questions