Filibuster, or how American democracy was paralyzed

As a consequence of the fresh midterm election, the majority in the Senate, regardless of the results of the complementary elections in Georgia, maintained the Democrats. Theoretically, it allows them to pass the bill more efficiently to the president. However, the legislature Republicans can make it hard for them, utilizing the alleged Filibuster. What is it, and how did it affect (and may inactive have) the passing of laws in the United States? ..