So put simply, Investiture is the power that makes Shards Shards and fuels all magic in the cosmere. So everything magical, from stormlight to the mists to Breaths to perpendicularities to basically any magic is all Investiture, and it can be used in different ways for different feats. It also has effects on people who hold a lot of it, like how someone of the Tenth Heightening warps colors and can see and hear more clearly. I agree with all the explanations before this, as well.
Look forward to seeing you around the forums!