This is the same as enabling a Tamil keyboard. The feature will be installed automatically if you add the Tamil language to your profile in Settings. Without this feature installed, Tamil is still supported on all Windows 10 systems using the Nirmala UI font, but some apps, Web sites or documents that require the other fonts might have issues.
There is one of these optional features, 'Supplemental Tamil Fonts', that includes the Latha and Vijaya fonts. In Windows 10, a number of these fonts have been moved into optional features. In the past, these used to be installed on all Windows systems. Out of curiousity, did you upgrade from Windows 7? Windows has a number of fonts that are designed for use with particular languages.
