I’m employed and self-employed uni student, how do I pay tax?

I’m a uni student and work at Tesco, I also have started doing Uber Eats as a side hustle for extra income. Just wondering, how does tax work? If I make a combined over £12750 a year, so for example £13000 at Tesco and £500 on Uber Eats, how would tax work for that? Or if I make £13000 at Tesco and £13000 for Uber Eats how would the tax work for that? Would the separate incomes be taxed at separate rates? Would I need to pay tax for UberEats if I made less than £12750 per year? Sorry if this sounds dumb just haven’t been educated on this before…

Hi Thombock,
Your income from Tescos will be taxed under the PAYE system.
If your Self Employed income from Uber Eats is less than £1,000 then this will be covered by the Trading Income Allowance.
If more than £1,000 you will need to complete a Self Assessment Tax Return.
The tax due would then be paid through the Self Assessment system.
Please see the following links for further guidance:
Trading allowance
Income Tax: introduction
Income Tax rates and Personal Allowances
Thank you.