Do I have to pay tax?

BR means Basic Rate and means you have 20% tax deducted from every penny you earn. If this is your only job, this is clearly incorrect and your code should be 1100L, which gives you your personal allowance of £11,000 a year before paying tax. Or there may be something else to affect it but in any case it should be a number followed by L. Tell HMRC you think the code is wrong https://www.gov.uk/government/organisations/hm-revenue-customs/contact/income-tax-enquiries-for-individuals-pensioners-and-employees

If this is not your only job and you're getting your allowance in the code on another job, then BR is correct.

Wrong tax code - go to gov.uk/income tax and read - you need to get your tax code corrected - this assumes you have no other employment.

Ask local adults for actual info locally as it varies greatly