The field of study aiming to make machines learn from new inputs automatically.
A computer program is said to learn from experience E with respect to some class of tasks T and performance measure P, if its performance at tasks in T, as measured by P, improves with experience E. - Tom Mitchell
Andrew Ng had a popular intro course to ML at Coursera. I took it in 2020 and at the time, I wrote down my notes on my blog.