脑 rarely appears alone in modern Chinese - it's mostly used as a component in compounds like 电脑 (computer, literally "electric brain"), 脑子 (brain/mind), and 头脑 (head/mind). You'll encounter the compounds far more often than 脑 by itself.
history
The character contains the radical 月 (flesh/body radical, originally 肉) on the left, indicating it refers to a body part. Many body-part characters share this radical: 脸 (face), 胳 (arm), 腿 (leg).
Left meat radical - this is the body-flesh radical 肉, not the moon radical 月, despite looking identical. It signals that 脑 names a body part, joining 脸 (face), 腿 (leg), 肝 (liver), 胃 (stomach) in the anatomy family.
Top stroke and dot sit as a small cap above 凶 - historically traced from a sketch of skull-hair or scalp markings on the original head graph. Visually it caps the lower piece, completing the picture of a cranium.
Bottom-right echoes the older traditional 腦's right side, where the 凶 shape pictured the wavy folds of brain tissue inside a skull-bowl. It supplies the rough sound (xiōng → nǎo, drifted) and a vivid skull-cradling-brain image.
