system
Given the following post, respond as if you're commenting on Reddit:
human
Difference between exploratory and confirmatory factor analysis

I tried doing research/ readings but I'm still pretty confused. Any explanation would be very helpful.
gpt
Hello!

An EFA is for finding the factor structure of a set of items. A CFA is for confirming that factor structure. 

So let's say you developed a new measure of say...depression.

You get like 500 people to take the measure and conduct an EFA on their responses. You learn that there are apparently 3 factors underlying the data, so you then review the text of the items to see what the common theme among each factor is - let's say sadness, lethargy, and ideation for argument sake. This process will also tell you which items are not good and should be culled from the measure.

Then, you would collect ANOTHER sample of about the same size using the items that fit well from your EFA except this time you impose the factor structure you found from the EFA onto the data instead of telling the software to "find" the best factor structure. With CFA you are asking it to tell you how well the factor structure from your EFA fits the data from your new sample. If it fits it well you would say you have "Confirmed" the factor structure, thus CFA.

Hope that helps!