There is a function named Alert() in MQL4. Here is how it works:
Alert("some text here");
or...
Alert("some text here"+", and some other text here");
or...
Alert(Symbol());
or...
Alert("my current symbol is: "+Symbol());
or...
Alert(""+Symbol()+"");
So, + is like glue, and you can put as many things as you want to display, one after another with + in between. Strings (texts) are always with " in the beginning and " in the end. Digits are not.
Alert(12345+"some text here");
will alert this: 12345some text here
Text in Condition outputs what is in the field, but it automatically puts " in the beginning and " at the end of it. So, if you write just Symbol() it will become...
Alert("Symbol()");
and this will alert: Symbol()
but Symbol() is a function and at the end it must be executed as such, something like
Alert(Symbol());
but because the generator puts " and ", then we need to do some thick until we have this:
Alert(""+Symbol()+"");
and this will output: EURUSD