The strength of your tiles will mostly be determined by their resistance grade and their thickness. Generally, the higher the resistance grade and the thicker the tile, the stronger it will be. Resistance grades go from Grade 1 to Grade 5
While there isn't a standard thickness for floor and wall tiles, most are at least a ¼ inch thick.
For areas with high traffic, get floor tiles that are between ½ inch and ¾ inch thick.
For wall tiles, you can get away with tiles even thinner than ¼, especially if they're decorative rather than functional tiles.
As far as the resistance grades go:
Grade 1 is the weakest resistance and is only suitable for wall tiles.
Grade 2 is another great option for walls and may be sometimes used in floors with relatively light traffic.
Grade 3 is the most common grade for homes as it can be used in higher traffic areas like kitchens without much wear.
Grade 4 can take a lot more foot traffic, so it's great for hallways. It's sometimes used in commercial areas like doctor's offices.
Grade 5 is the most heavy-duty, used in airports and shopping malls, and is a bit of an over-kill for home tiles.