An alloy is a mixture of two or more elements that are combined in varying proportions.
A mixture can be categorised as a homogenous or heterogenous.
A homogenous mixture is one in which the different components have the same composition throughout and exist in a single phase. In contrast, in a heterogenous mixture, the components have varying composition and might not be evenly blended to form a single phase.
In Sterling silver 93% silver along with 7% other metals are uniformly mixed to form a homogenous mixture.