Atheists and theists.

Approximately 24.2% of the world's population is religiously unaffiliated, while 75.8% identify with a religion. 

Among those with religious affiliations, Christianity is the largest with 31%, followed by Islam (24%), Hinduism (15%), and Buddhism (7%). 

The religiously unaffiliated include atheists, agnostics, and those who do not identify with any particular religion. 

Here's a more detailed breakdown: 

Religiously Unaffiliated:
This category, also known as "nones," includes atheists, agnostics, and those who don't identify with any religion. 

Christianity:
The largest religious group globally, with 31% of the world's population identifying as Christian. 

Islam:
The second-largest religion, with 24% of the world's population identifying as Muslim. 

Hinduism:
A major religion, with 15% of the world's population adhering to it. 

Buddhism:
A significant religion, with 7% of the world's population identifying as Buddhist. 

Other Religions:
A variety of other religions and indigenous faiths account for the remaining percentage of the global population. 

It's worth noting that the percentage of religiously unaffiliated people is growing, while the percentage of those affiliated with specific religions is decreasing.