Complex sentence: Different types of brain tumour are generally described as being either benign and malignant-the latter being capable of spreading to other regions of the brain and central nervous system, the former tending to stay localised at the site at which they initially arise.
Split into simpler sentences: Different types of brain tumour are generally described as being either benign and malignant. Benign tumours tend to stay localised at the site at which they initially arise.