question mark in code means what?

hi, i've got this code containing a certain line in which i see a question mark and haven't got the slightest of what it means.

 protected void Button1_Click(object sender, EventArgs e)
{
int total = 0;
for (int i = 0; i < TextBox1.Text.Length; i++)
total += char_gematria(TextBox1.Text[i]);
TextBox2.Text = (total == 0) ? "" : total.ToString();
} 10x ...