Being invited to an assessment centre is brilliant news because it means that you have made it through to the later stages of the recruitment process. It is often the last part and employers make their job offers based on the performances of the candidates at the assessment centre. However, for some companies there may be a further stage at a later date, such as interviews with senior managers, for those who have passed the assessment centre. Whichever stage it is, you are being given the opportunity to actually meet the employer and to show them your worth.
You will probably feel quite excited at being invited to an assessment centre but also find the thought of it rather nerve-racking. You may have never been to an assessment centre before but, even if you have, you will be keen to impress the employer so the key message is to prepare really well.