Getting istio & istio-pilot Services When Installing istio1.5

When Installing Istio 1.5 (any Configuration Profile).Got a namespace Istio-system. In which multiple services and pod exist. out of them there are 2 service in which i have a confusion i.e. istiod and istio-pilot.
Cn anyone clear my doubt. Why we use 2 differrent sevice for same pod i.e. istiod.