What is the evil eye in Islam?

Is the evil eye real in Islam?

Yes. The Prophet ﷺ said, "The evil eye is real" (Sahih al-Bukhari 5740). In another narration he added that if anything could outstrip destiny it would be the evil eye, and that if you are asked to wash for someone affected, you should do it (Sahih Muslim 2188). Many scholars also see a reference to it in the Quran, where the disbelievers almost "make you slip" with their stares:

How does it happen?

Scholars explain that the eye itself has no power. Harm happens only by Allah's decree, but He made the envious or even admiring look of a person a cause, the same way He made germs a cause of illness. Surprisingly, it doesn't need bad intentions: a loving parent or a close friend can cause it by admiring something without remembering Allah. That's why the Sunnah is to say "Masha'Allah" or "Barakallahu fik" when something impresses you. See What do I say to avoid the evil eye when I like something?

How do I protect myself?

• Daily adhkar. Ayat al-Kursi and the last three surahs (al-Ikhlas, al-Falaq, an-Nas) in the morning and evening.
• Ruqyah. Aisha reported that the Prophet ﷺ told her to use ruqyah against the evil eye (Sahih al-Bukhari 5738). You can recite it over yourself. See What is ruqyah and can I do it myself?
• Some privacy. You don't have to post every blessing, new car or baby photo online. See Can I post photos of my kids on social media as a Muslim?

What about nazar beads and charms?

The blue eye pendant, the hamsa hand and similar charms are popular in many countries, but scholars warn against them. Hanging an object and believing it protects you means relying on something other than Allah. Protection comes from Allah through dua and the Quran, not from beads. Also, don't fall into the opposite trap of blaming every exam result or argument on the evil eye. Most problems have normal causes, and illness needs a doctor, too.