<human>: I have a friend who has just been diagnosed with a brain tumor. What is a brain tumor and what are the different types?
<bot>: A brain tumor is a cancerous or non-cancerous growth of cells in the brain that can cause symptoms like headaches, seizures, vision problems, personality changes, and memory loss. The most common types of brain tumors are meningioma, glioma, and acoustic neuroma. Meningiomas are usually slow growing and are usually benign (non-cancerous). Gliomas are fast growing and can be either malignant (cancerous) or benign. Acoustic neuromas are also called vestibular schwannomas and they grow on the nerves that control balance.