FSCS is a scheme put in place to protect you if the current account provider you use was to go bust. The Financial Services Compensation Scheme will ensure you'll be able to receive £85,000 per individual account or £170,000 if it's a joint account (an account used by more than one person.)
This scheme covers banking groups that have a license; however, be cautious that multiple banks and brands may only be under one license.
Suppose the HSBC group - which only has one license across its brands - was to go bust, and you have a current account with HSBC and First Direct, (their two UK brands). In that case, you'll only get £85,000 protection across the two accounts, not £85,000 for each.
FSCS can also be used to claim from pension providers, bad mortgage advice, and PPI claims.