If you go northeastward, you go towards the northeast — the direction that sits between north and east. People use it after a verb of movement: the storm moved northeastward; the path runs northeastward. They also put it in front of a noun: a northeastward wind, a northeastward route. It is a little more formal than just saying northeast or to the northeast, so you meet it in weather reports, maps, and careful travel writing. American English likes this form without an extra s. British English often says northeastwards for the same idea. Though actually, northeast by itself already does a lot of this work — We drove northeast is perfectly normal — and the -ward only makes the towards feel extra clear. It is a direction of travel, not a place you can stand in.

向東北；往東北