What type it is:
Product: Sledge Hammer or Club Hammer
Handle: Fiberglass with rubber grip - the white/teal and orange/black ones
Head: Forged steel square/rectangular head
From the size in your hand, these look like 2lb - 4lb club hammers. Not the big 10lb+ sledge hammers.
What they're used for:
1. Demolition - Breaking concrete, bricks, tiles
2. Driving - Hitting chisels, wedges, stakes, masonry nails
3. Metal work - Forging, straightening, shaping metal
4. Construction - Tamping, breaking, heavy striking where a claw hammer is too light
5. Automotive - Panel beating, separating stuck parts