This is usually done to avoid interrupting fluency practice, although there are other reasons also. Delayed correction contrasts with correction techniques such as reformulation and echoing, which occur immediately, 'on the spot'.
Example
The teacher monitors closely as learners discuss a topic in groups, making a note of the most interesting/important errors. When the discussion finishes, these are discussed open class.
In the classroom
The decision whether to correct immediately or not depends on various factors. These include aims, class dynamics, learner attitude and expectations, motivation, level, and the teacher's evaluation of whether a mistake or an error has been made.
Further links:
https://www.teachingenglish.org.uk/article/monitoring-speaking
https://www.teachingenglish.org.uk/article/teacher-talk-error-correction
https://www.teachingenglish.org.uk/blogs/george-chilton/george-chilton-we-all-make-mistakes