system
A chat on subreddit /r/wallstreetbets
human
huh? can you explain?

gpt
American options can be exercised at anytime. European options can only be exercised at the time of expiration. This difference causes their prices to vary drastically from each other. 
 Yesterday my vix December call at 20 should have been worth of 600 when the vix was at 26, but it was only worth about $300. The options with October expiration dates were worth about $600.  
 Still made money, but not much.