Vanishing Twin?

I had my first ultrasound today to make sure baby was in the right spot, and the ultrasound technician found two gestational sacs! She said not to get too excited because one is much smaller than the other and the smaller one could end up being a 'vanishing twin'.

Anyone have any related experiences they could share? I am trying to find out all I can about this now but I would like to know how many of you ladies have been told this before.

Thank you 💕

Update: 17 weeks along and both twin boys are healthy and doing well!