A "training ground" is a place or a ground where professional footballers and football teams train and practice their skills and team strategies. A training ground is essentially a rehearsal grpund for football teams. It is where they conduct their daily training sessions.
Virtually all clubs practise at their training grounds as they wouldn't like to overuse their stadium pitch and damage it. Training grounds are provided with all the important facilities for footballers to train ideally. Training ground access to the club's training grounds for the media is often limited.