If you're just getting familiar with school performance data, read this article to understand the basics.
Understand the difference
Here's how the Department for Education (DfE) and Ofsted use these terms:
Attainment: the academic standard that pupils reach in, for example, assessments and exams. It's usually recorded as grades, scores or levels, and it indicates a pupil’s result at the end of a Key Stage (KS).
In other words, attainment is where a pupil is at a specific point in time, and progress is how steep the climb was between attainment points. The steeper the climb, the greater the progress. You need to look at them together to get a clear picture