A run time error will only occur when the code is actually running. These are the most difficult – and lead to program crashes and bugs in your code which can be hard to track down.
An example might be trying to convert a string: “hello” into an integer:
string helloWorld = "hello"; int willThrowRuntimeError = Convert.ToInt32(helloWorld);
The compiler may not see this as a problem but when run an error will be thrown.
Compiler errors are due to inaccuracies in code, where the compiler throws an error to alert you to something which will not compile, and therefore cannot be run.
An example of a compiler error would be:
int = "this is not an int";
Hope that helps.