When one action "leads to" another action, it's similar to causing something to happen. But it happens over a long period of time (months or years). This phrase is useful for talking about health problems:

Obesity can lead to heart disease.

Marijuana use often leads to more serious drug addiction.

It can also be used to talk about scientific research:

We're hoping that our research will lead to improved cures for victims of skin cancer.

And the environment:

Carbon dioxide emissions have already led to an increase in the world's average ocean temperatures.