When you get sick, your white blood cells fight the harmful germs with special germ killers called antibodies.
White cells manufacture antibodies for each particular sickness, so if you have chicken pox, your white blood cells make chicken pox antibodies.
After you are recovered, these antibodies stay in your blood and keep killing any chicken pox viruses that get into your body. That is why you can’t get chicken pox twice.
You have become immune to it.
In the same way, when you get a cold from a cold virus, your body makes antibodies to fight that particular cold virus. You can never get a cold from that particular kind of virus again.
However, since there are more than 200 different kinds of viruses that can cause colds, a new cold virus can enter your body and you will not have antibodies in your blood to fight it.
Then you will get another cold.