How does a spacecraft change course?

What are vectors?

A vector is something that mathematicians and engineers use to represent or calculate a force that has direction. The vector will show the direction of the force and the size of the force as well. Sometimes vectors are represented by arrows, with length or thickness of the arrow representing force, and direction representing direction. Sometimes vectors are represented by sets of numbers.

Often vectors are used in spacecraft navigation. The engineers know where they want to go and use vectors to figure out what direction to thrust in to go there.

What is a course correction?
How does a spacecraft get to where its going?
How do scientists know what the path of an object in space will be?

How can we tell a spacecraft's speed?
What is thrust?