The へ particle indicates that one is heading or setting out to head towards a goal or direction. The へ particle is often confused with the に particle and for a good reason. The へ and に particle can somtimes be interchangeable and yet produce a slighly different meaning. に is used when the destination is the final goal. However へ does not necessarily mean that the destination is the final goal. に is much more specific. It’s kind of like saying, “I will go TO the (actual location of the station) station”, but へ is more ambiguous, more like “I will go TOWARDS the station (but perhaps not at the actual station but somewhere outside it)”.

There are times when に and へ are interchangeable. For example the sentence used above is interchangeable, with only a slight (depending on the context) difference in meaning. “えき　に　いきます” = I will go to the station. “えき　へ　いきます” = I will go towards the station. (えき = station. に/へ = ni/he particle. いきます = will go.) Also most of the time へ is pronounced as “he”, but as a particle it is pronounced as “え“. Obviously when you’re giving directions to someone, the distinction of に versus へ is important, but the general understanding of the sentence (not including giving directions) of the two particles are similar.

に and へ are not interchangeable in terms of time. Only に is used for time references. (For more on the に particle, check the blog post here: https://blogs.transparent.com/japanese/%e3%81%ab-particle/) For example, a sentence like this is correct with に but not with へ: “ろくじ　に　たべます” = I eat at 6 o’clock. (ろくじ = 6 o’clock.　に = ni particle.　たべます = eat.) へ cannot be used in this sentence because 6 o’clock is an exact time reference. If you want to say something less exact like “I eat around 6 o’clock” use the word ごる like this, “ろくじ　ごる　たべます”

Another restriction on へ is that you must use it with a verb of motion like いく (to go) or with a destination. For example, a sentence like this can only be used with に and not へ, “わたし　の　せんせい　に　あいます” = I will meet my teacher”. (わたし = my.　の = no particle.　せんせい = teacher.　に = ni particle.　あいます = will meet). Since あいます is not a verb of motion like かえる (to return) you can’t use へ. However you can say, “ぎんざ　へ　せんせい　に　あいます” = I will meet [my] teacher (somwhere in) Ginza. (Ginza = ぎんざ.) If you were to replace に with へ it would mean, “I will meet [my] teacher (at a predestined/agreed upon destination with the teacher in) Ginza.