VIDEO : Avengers 4: What Are The Skrulls?

Avengers 4 is almost a year away.
Fans have no idea what to expect after the devastation in Avengers: Infinity War.
A lot of fans think the next Marvel storyline will be 'Secret Invasion.'
The 'Skrulls' are a big part of that storyline.
But what exactly is a 'Skrull'?
They're imposters.
Some Marvel characters in key positions of influence or power have actually be Skrull impostors for years.