Straight from documentation:
"Generate summary statistics of all existing fields in your search results and save them as values in new fields. Eventstats is similar to the stats command, except that aggregation results are added inline to each event and only if the aggregation is pertinent to that event."
Also, here are the link to the documentation files for stats and evenstats respectively:
There is no such thing as a question too "noob" but do try to do a little research before asking.
To be honest, I've used splunk for 3 years now and I still find the documentation to be pretty opaque at times - especially when you get into some of the less common commands like eventstats and streamstats. So I wouldn't worry too much. Do consult the docs before asking, but if you don't understand 100%, don't feel bad.