In this task, we ask you to elaborate the sentence without changing its general meaning. You can do so by explaining further the input sentence, using more precise wording, adding qualifiers and auxiliary information etc.

Let me give you an example: The Inheritance Cycle is a series of fantasy books written by Christopher Paolini.
The answer to this example can be: The Inheritance Cycle is a tetralogy of young adult high fantasy novels written by American author Christopher Paolini.
Here is why: The output sentence elaborates on the input sentence without changing its general meaning e.g. "tetralogy of young adult high fantasy novels".

OK. solve this:
The UEFA Champions League is a football competition between the best club teams in Europe .
Answer:
The UEFA Champions League ( abbreviated as UCL ) is an annual club football competition organised by the Union of European Football Associations ( UEFA ) and contested by top-division European clubs , deciding the best team in Europe .