A screen image is formed by an  electronic back lit display whereas a print is a reflected image produced on one of many paper types. Each has it's own unique colour gamut and other in-built variables.

The way a picture appears on your screen depends on your screen settings like contrast, brightness, profile and the same picture may appear differently on different screens. It is therefore crucial that your monitor is correctly calibrated/profiled to provide the best chance of colour accuracy.

The same unadjusted image printed on different media can often appear differently as well.

It is possible to achieve a close screen/print match but for optimum colour fidelity proofing is absolutely crucial.