Centigrade (or Celcius) is the name of the unit for temperature. 

So, for example, a hot day may have a temperature of 'thirty degrees centigrade' .This means the same as 'thirty degrees Celcius'.

We shorten this to: 30 °C and you can read the temperature on a thermometer.

Need to know more?  Back in 1742, a scientist Anders Celcius measured the temperature of melting ice (0°C) and boiling water (100°C) at standard atmospeheric pressure.  He placed these on a scale and divided the scale into 100 equal units of temperature.  He called each unit these one degree centigrade.  By 1948, everyone agreed to call it the 'degree Celcius' instead of the 'degree centigrade'. 

Of course, these days, the two ends of the scale, 0°C and 100°C, are measured much more accurately.  If you want to find out about the Celcius temperature scale, or the Fahrenheit temperature scale, click on the link below.