The Russians deploy forces near their borders to intimidate, and sometimes (Georgia 2008 and Ukraine 2014) as a cover for an invasion. Ukraine has responded by declaring martial law for a limited time.
In Standoff With Russia, What Does Ukraine’s Martial Law Decree Mean?
This could have an impact on Ukrainian elections (now set for March 31, 2019), since elections cannot be held within 30 of a martial law being in effect.
Right now, Petro Poroshenko (incumbent) is looking to change current trends (incumbents normally lose in Ukrainian presidential elections), so opposition parties are crying "October surprise."
The Russian forces have been there for a few weeks, but I would be surprised if they invaded Ukraine. The Russian army relies heavily on conscripts and they conscript in October and April, so October draftees would not have had enough time to finish basic, get to units and learn their jobs. They won't be ready until mid to late January.