へ details

へ

to; toward — points a movement at where it is headed

この電車でんしゃは空港くうこうへ行いきますか。

kono densha wa kuukou e ikimasu ka.

Does this train go to the airport? neutral

お母かあさんへ、いつもありがとう。

okaasan e, itsumo arigatou.

To Mum — thank you for everything. casual

Examples

direction — へ aims the movement at a goal without claiming it was reached

この電車でんしゃは空港くうこうへ行いきますか。

kono densha wa kuukou e ikimasu ka.

Does this train go to the airport? neutral

そろそろ会場かいじょうへ向むかおうか。

sorosoro kaijou e mukaou ka.

Shall we head for the venue soon? casual

詳くわしい資料しりょうはのちほどご自宅じたくへお送おくりいたします。

kuwashii shiryou wa nochihodo go jitaku e o okuri itashimasu.

We will send the detailed materials to your home address later. formal

the addressee — へ heads a letter, a parcel or a dedication with the person it is meant for

お母かあさんへ、いつもありがとう。

okaasan e, itsumo arigatou.

To Mum — thank you for everything. casual

への — への is the の-form に has no way to make, so 母ははへの手紙てがみ works where ×母ははにの手紙てがみ does not

Written へ but read え, the way は in the same slot is read わ and を is read お.

に
Interchangeable on a verb of motion or transfer — 京都きょうとへ行いく and 京都きょうとに行いく are both ordinary — because へ names the direction taken and に the point reached; where に names a point, a time or the second argument a verb requires, へ is out (三時さんじに, 先生せんせいに会あう, 家いえにいる), and even arrival leans に (駅えきに着つく).
に向かって
に向むかって marks orientation with no motion at all, which bare へ cannot — 窓まどに向むかって座すわる is ordinary where ×窓まどへ座すわる is not, so a verb that only faces a direction rules out the bare particle.