Please educate me, I know nothing about it at all.

https://www.maths.cam.ac.uk/undergrad/admissions/step

"Achievment in the Sixth Term Examination Papers (STEP) normally forms part of a conditional offer to read mathematics at Cambridge. The examinations are administered by the Admissions Testing Service (which is part of Cambridge Assessment, the parent company of the OCR examination board) and are taken in late June."

Schools normally support their students with additional lessons and there are online support websites such as https://maths.org/step/welcome

TSR also has a STEP preparation thread.

Roughly 50% of Cambridge maths offers are missed because the STEP requirements are not met so they have to be taken seriously.

https://www.admissionstesting.org/for-t ... bout-step/