u/Efficient-Durian-452

Moved into our new home and noticed cracks between tub and tile (also noticed an ant or two crawling from it). I was going to it but when removing noticed the gap was much larger and material was much harder than I expected. Am I supposed to caulk or grout this gap? Do I need to fill the entire gap?

Edit: it’s outside of the tub where it meets the floor tile.