What financial instrument is considered an "improvisation" over forwards?

What is the term for the minimum quantity specified in a futures contract?

How are equity futures contracts settled?

What is the term for the daily adjustment of profits or losses in futures trading?

What is the primary purpose of margins in futures trading?

What is the term for the margin that must be maintained in a trader's account to avoid penalties?

What happens when a trader's account falls below the SPAN margin requirement?