person A: I recently took my ELS certification test. I studied really hard_comma_ so I'm sure I passed it.
person B: What's ELS?
person A: Sorry_comma_ ESL. It's English as a Second Language. It just means I am certified to teach students that don't speak fluent English.
person B: Ah_comma_ gotcha. A few of my friends teach English to Chinese students online and I think they have taken ESL courses