To Be Boiled
To Be Cooked
intransitive verb, ichidan verb
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb.
You already learned 煮る, which is used for when you purposefully boil something. This verb, on the other hand, is intransitive, meaning that it refers to when something is getting boiled or cooked up, with no emphasis on who put the thing in the pot. That's why this verb means to be boiled or to be cooked.
Since this word has okurigana (hiragana attached to the kanji) you know that it's probably going to be the kun'yomi reading. You learned this reading with the kanji. Good for you!
豆、ちゃんと煮えてる？
Are the beans cooked well?
さて、そろそろジャガ芋が煮えるころだ。
Well, it's about time that the potatoes should be cooked through.
鍋の中には怪しげなスープがグツグツと煮えていた。
There was a mysterious soup gurgling and boiling in the pot.