"Fortnite" is often compared to another popular shooter, "PlayerUnknown's Battlegrounds." There's good reason for that: They're very similar.
The first thing you do in "Fortnite" is jump out of a purple flying bus and parachute down to an island. The island is full of distinct regions, and it's littered with resources: Guns, explosives, med packs, shields, and various materials (wood, brick, metal).
With nothing other than a pick-axe, you desperately need resources to survive. This is a nearly direct mirror of the experience in "PlayerUnknown's Battlegrounds."
But there are major differences right off the bat. Rather than simply picking up weapons and healing kits, "Fortnite" also has a construction element to it. Thus why you're picking up materials — stuff like wood, brick, and metal. Alternatively, you can use your pick-axe to mine the materials yourself, like you would in "Minecraft" (as seen above).
The world is destructible, so with every swing of your pick-axe you'll wear down whatever object you're striking — whether it's a tree or a brick wall.
There are loads of parallels between the two games, but "Fortnite" is immediately distinguished by this crucial difference.