Always
Constantly, Continually
adverb
The particle に here is a clue that this word is an adverb. An adverb describes actions, so what's a normal action? It's one you're always, or constantly, doing. That's what makes it normal!
The reading is the kun'yomi reading, which you didn't learn. In order to learn it, think of this:
I always tune (つね) my violin, but today I didn't tune it. So, now I sound terrible. Imagine how terrible my untuned violin sounds, compared to how it always sounds.
彼は常に笑顔です。
He is always smiling.
私の母は常に走っています。
My mother is always running.
自分の親が常に正しいわけではないことを知るのに、時間がかかる子どももいます。
It takes some kids a while to realize their parents aren’t always right.