A bank is a commercial, licensed financial institution that securely holds money people deposit into it. The bank pays interest on money it holds and also lends money out in the form of loans.
Credit Unions offer many of the same services as banks, such as savings accounts, loans, etc. But Credit Unions are owned and run by their members, for the benefit of those members.
Some Credit Unions have different rules for loans.
A person who may be denied a loan at a bank, may be granted a loan at a Credit Union, if they are a member.