Why is there acceleration when there is a change in direction?

so what is acceleration? It is change in velocity i.e. change in velocity/time. But why do acceleration change when I change direction? Suppose I am moving with 30 km/hr and I took a right turn at 30km/ hr, so why does acceleration change? That literally makes no sense:/.why is acceleration not scalar quantity why is it vector ?my head hurts:/ only serious discussion please, no trolls