Commission
A flat per-lot fee on ECN accounts. In exchange for near-zero spreads.
ECN brokers charge round-trip commission (open + close) in exchange for much tighter spreads. Standard accounts charge no commission but wider spreads. Often ECN nets cheaper at typical retail size.
Related
Learn to actually use Commission.
Definitions are the easy part. The free first five modules put this on a real chart and make you do the work. No card required.