Universities in the United Kingdom use a centralized system of undergraduate application: University and College Admissions Service (UCAS). It is used by both domestic and international students. Students have to register on the UCAS website before applying to the university. They will find all the necessary information about the application process on this website. Some graduate courses also require registration on this website, but in most cases students have to apply directly to the university. Some universities also accept undergraduate application through Common App (the information about it could be found on universities' websites).
Both undergraduate and graduate students may receive three types of responses from the university. The first one, “unconditional offer” means that you already reached all requirements and may be admitted to the university. The second one, “conditional offer” makes your admission possible if you fulfill some criteria – for example, have good grades on final exams. The third one, “unsuccessful application” means that you, unfortunately, could not be admitted to the university of you choice.
All universities require personal statement, which should include the reasons to study in the UK and the information about personal and professional goals of the student and a transcript, which includes grades received in high school or in the previous university.