へ (E) is used to indicate an action's recipient. へ always conveys the concept of a physical or abstract direction. The particle に (NI) can also be used in this case, but expresses the destination rather than the direction.
NOTE: へ is the hiragana for HE, but the H is never pronounced when it's the particle!
中村さんへ請求書を送りました。
Nakamura san e seikyuusho o okurimashita.
I’ve sent the invoice to Mr. Nakamura.
2.
The particle へ (E) is used to indicate a direction or goal someone is moving towards. The particle に (NI) can also be used in this case, but expresses the destination rather than the direction.
NOTE: へ is the hiragana for HE, but the H is never pronounced when it's the particle!