IDE Check, what is it's pourpose

Sever times I have used the “Check” button and it says Success…
Yet there are errors in it. I have tired this many, many times on all kinds of code, and it says the same thing. Yet when I run the code the log window shows an error. So what is the purpose of the check button ?

Some Squirrel errors, such as syntax errors, can be detected when compiling the code. These “compile-time errors” are what the “Check” button finds. Other errors, such as missing functions or mis-spelled variable names, can’t be detected just from inspecting the code. These “run-time errors” are the ones that appear in the log window.