Trump's tweets count as an 'overt act' in the Georgia case. What does that mean?

https://www.npr.org/2023/08/17/ [login to see] /trump-georgia-indictment-rico-tweets-charges
The indictment in Georgia against former President Donald Trump relies heavily on the state's Racketeer Influenced and Corrupt Organization law — a statute generally used to prosecute mob bosses and gang members.

Fulton County District Attorney Fani Willis centers her case on the idea that Trump and 18 others worked together "knowingly and willfully" as part of a broad conspiracy to attempt to overturn the 2020 presidential election results.

As part of this conspiracy, prosecutors claim, the 19 defendants committed a total of more than 160 individual "overt acts" to further their plan. Those actions include tweets and speeches made by Trump and others, phone calls and meetings.