Stemming vs Lemmatization

How is stemming and lemmatization different?

Stemming work on single word without knowledge of the subject. Stemmers are easier to implement and faster to run.

Lemma of a word changes with context and hence are difficult to implement. ‘Running’ has ‘run’ as it’s lemma as well as stem. ‘Better’ has ‘good’ as it’s lemma but not stem.