In terms of lesson planning ESA stands for engage – study – activate. This is one example of a way to structure and plan lessons.
Engage refers to getting the students’ attention, interest and involving them emotionally. This can take the form of a warm-up activity, game, story or anything that stimulates them. If emotionally involved, the students are more open to the learning process.
Study is the time where the focus is on a language point. This could be vocabulary, pronunciation, grammar, analysis of language in a text…. This can be the teacher explaining, students working out rules for themselves in groups, etc. Students feel comforted when there is some aspect of language focus. It’s part of their expectations of learning.
Activate refers to the use of language. This means using it in a realistic context, as close to real-life as you can get it. Try to incorporate activities that have students using any language freely and not focussed on one structure. This is important preparation for speaking in the real world.
You can have all three ESA stages in one lesson but they don’t always have to take place in this order. You can engage and activate and then study language points arising from the activate section. You could also have a lesson wholly dedicated to an extended speaking activity. In this case you would engage and activate. The study part could take place in the previous lesson or the following lesson. If afterwards, you would focus on language points that were a problem in the “activate” part. The important point is to always engage students. Lessons can also have various sequences of ESA, especially at lower levels where activities tend to be shorter.