When you mend something, you fix it or make it better. If you can mend your broken lamp, then it will shine again. If not you'll have to sit in the dark.
The word mend was originally used as a religious term, meaning to free a person from sin, usually through repentance and good deeds. Mend has come to refer to fixing something that is broken. A mechanic might mend a broken car, or a seamstress might mend a torn dress. The word also frequently relates health and healing. Someone recovering from a long bout of the flu is said to be "on the mend." But as the song goes, "How can you mend a broken heart?"