It's a tip pool. So for instance I serve a meal to a couple. The meal is $50. They tip 10%. That split means I pay (for instance) the bartender out of the $5 tip $2.50. If I get another table that orders drinks and tips nothing I end up splitting nothing. But if I work with 4 other back of house people and they each get an equal percentage of that $5 then I get a dollar. But then that dollar is taxed because tips are taxed. If the company has a policy for shares tips pooling I could legitimately make $100 in tips and not receive $100 in tips. Technically that would be receiving negative tips because what is earned vs what is paid out is so drastically different.

In addition I've experienced back of house workers (cooks) getting paid out of the tip pool but the brunt of tax on the tips is not paid by them. This is absolutely tax fraud. But I'd also argue that tip pools are a form of wage theft and companies that engage in one are way more likely to engage in the other.