SATs (or Standard Assessment Tests) are national tests given to children at school. They are also known as 'SATs papers', 'SATs exams' or 'SATs tests'.
In primary school, children take their Key Stage 1 (KS1) SATs at the end of Year 2 and their Key Stage 2 (KS2) SATs at the end of Year 6. SATs papers are taken in English Reading, Maths and Grammar, Punctuation and Spelling (GaPS or SPaG). Separate SATs papers are also taken in Writing and Science though these are less formal teacher assessments.
Here's access to free past SATs papers: Download here