It is an Aucuba leaf Croton so-named because of its similarity to the Acuba, which is a different plant species.
It looks lie the older lighter colored leaves are dropping because it is not getting maximum light. The newer growth is a darker green color. That's fine, but yours will adapt to the reduced light by dropping older leaves. Best to provide as much direct sun on your sunniest windowsill as possible.
Ordinarily you should water as soon as the surface of the soil feels nearly dry, but yours is in a pot that is a tad too big, so you will need to allow the top half-inch to deary before watering thoroughly, regardless of the season
High humidity helps, but is not essential as long as watering is done properly. Warm. dry air will encourage the reproduction of spider mites, which love Crotons, so be vigilant for mites. Cool house temperatures are best for Crotons.
As it grows taller, it will become leggy. However, it can be pruned back when that happens.
Will Creed
wcreed@HorticulturalHelp.comMy website