Phase- It is defined as any homogeneous, physically distinct and mechanically separable portion of a system, which is separated from other such parts of the system by definite boundary surfaces.
(i) At triple point in water system, three phases co-exists.
ICE (solid) ⇔ Water (liquid) ⇔ Water vapours (gas)
(ii) Miscible liquids like ethyl alcohol and water will form one liquid phase only.
Component- It is defined as the smallest number of independently variable constituents taking part in the state of equilibrium by means of which the composition of each phase can be expressed directly or in the form of chemical equation.
(i) In water system: Chemical composition of all three phases (ICE-Water-Vapours) is $H_2O$
∴ It is one component system.