A glioma is a brain tumor arising from a certain type of cells – the glial cells. Glial cells (from glia, which is Greek for “glue”) form a supportive and protective layer for nerve cells and insulate nerve fibers so that electrical signals are not passed on unregulated. There are different glial cells that tumors can develop from. The type of cell most like the tumor cells also determines the name of the tumor. Gliomas are relatively rare.