Both the Cold and flu are respiratory illnesses but they're caused by different viruses.
The flu virus is worse than the common cold virus and makes you feel more weak and ill than the cold virus does.
When you have a cold you're more likely to have a runny nose or even a stuffy nose and feel congested and you don't usually have the chills with the cold virus like you do with the flu virus.
Usually a cold virus doesn't cause a fever like the flu usually does but it can sometimes cause a fever.
The flu also causes body aches, muscle pain, fever, headaches and sometimes watery burning eyes.