へ after a place marks where a movement is headed: "to". As a particle it is read "e", not "he". The verb is usually one of going, coming or going back.
With verbs of movement へ and に both mark the destination, and you can use either.
へ leans towards the direction you set off in, に towards the place you arrive at. In everyday sentences the difference is too small to matter.
に has jobs that へ does not share: it also marks a time and the place where something is.
The particle sounds like え and is always written へ. Inside a word へ keeps its usual sound: へや (room) is "heya".
These go beyond the plain destination.
へ also follows a word for a direction rather than a place.
へ can mark the person a letter or a present is going to. It is how a card or a message is addressed: たなか田中さんへ, "To Tanaka".
Before の, only へ is possible: はは母へのてがみ手紙 is "a letter to my mother". に cannot stand in front of の.