The sanctions are based on H.R.3364 - Countering America's Adversaries Through Sanctions Act, which was passed on last July and signed into law on August 2nd. It gave a timeline of various actions required by various executive departments including the Treasury, and the President himself. Most of the act is supposed to have been implemented after 180 days.
The Treasury department, in consultation with the office of the DNI and the State Department, only managed to submit their required reports near the end of January, with no actual sanctions being implemented by then. The report featured 96 individuals in regards to the Russian portions of the act, with many of them being various Russian oligarchs or government figures closely affiliated with Putin (though it's sort of redundant to say that I guess).
The list of entities and individuals in the sanctions today instead is mostly made up the people and groups Mueller indicted this past February 16th, who already facing greater legal jeopardy since they're going to be arrested if they ever go anywhere the US has jurisdiction or an extradition treaty. The other targets are associated with Russian military intelligence.
In summary, the sanctions are late, and the actions today pretty much ignored the Treasury's own reports in favor of targeting one Russian troll farm and some people associated with the Russian version of the CIA. As far as economic and political impact goes I would guess it would be trivial in Russia given the targets chosen. They are basically the most direct (and thus low level) agents involved in the election interference, with quite a bit of redundancy because of the Mueller indictments and the fact that Mueller hasn't been shy about using asset forfeiture. Domestically it could be used to say that the administration is doing something about Russia; how well that goes over remains to be seen.