GCSE is some kind of educational qualification - I think it's like a high school certificate or some such you get after passing tests at the end of your 12th year.
@badarnawazkhan - don't stress about it. Worst case you can repeat the year, best case you passed. Good luck.
I vaguely remember GCSEs (am 26 now). In honesty didn't put in as much effort as I should have and came out with 'ok' results. Went on to Sixth Form/College and failed A-Levels so got a job. Currently working in IT Contracting in a very prestigious company on great money.
I am guessing you are young, but really, in the greater scheme of things nobody cares if you repeat a year or not, and by the time you hit 30, you wont care either - Or rather, you wont care if you've managed to get yourself a good education and you're doing a job that you love, otherwise your own regrets are your own to live with.
This is my point. There is no need to stress. A prospective employer isn't going to look at a resume and factor this any other way than as a positive - and if they do, you don't want to be working for them anyway.