Biologically race can be human groupings with physical differences. But if such differences trigger preconceived notions about certain groupings then this is racial ideology. This defines the social concept of race.
According to them race is "a pre-eminently sociohistorical concept. Racial categories and the meaning of race.. have varied tremendously over time and between different societies." (Omi, Michael and Winant, Howard. Page 287)
Race today is "assumed to be a variable which is shaped by broader societal forces." The concept varies from society to society. 'Blacks' in the contemporary British politics refer to all non-whites. In the United States 'havin' a little Negra blood' makes one non-white.
Biological definition and social concept of race do make a lot of difference. Omi and Winant distinguish them as "natural" and "common sense." Having a particular skin tone or hair is one's racial identity, but branding him or her as black or Hispianic or white is racial ideology. ...