How do realtors get paid on rentals?

I inquired about an apartment in zillow. A realtor contacted me and she then found more places for me to look at and took me around. I didn t pay her anything so how does she get paid?

What s confusing is I could have just contacted the leasing office myself and didn t really need her, so in that case, why would the leasing agent pay my realtor? People can just call the leasing office themselves ...