What does spotting look like?

So it's possible to still be pregnant if you have a period but it's lighter than normal ? 
I had a period that lasted two days and was very light.. Then vanished ... Then two days later I bleed a little and it was gone again I really didn't think anything of this cause I thought it was just my period being weird... Is that spotting that occurred ? 
What does spotting usually look like? 
I doubt I'm prego but should this worry me?