Here's the short explanation.

A filibuster is a Senate rule which effectively allows the minority party in the Senate to require a super majority of 60 votes to pass legislation instead of a simple majority of 51 votes. Since the senate is typically split very closely between the two parties, it forces each party to convince at least a handful of Senators from the opposing party to vote for their legislation, or it will not pass.

Without the filibuster rule, whichever party controlled the senate could completely control everything happening in the senate without opposition from the minority party.

Here's a technical explanation of the filibuster. It's an interesting "parliamentary" feature of our democracy dating back to 1917.

https://www.brennancenter.org/our-work/research-reports/filibuster-explained

Colorado was trying to have Trump removed from the ballot as a presidential candidate in the state of Colorado. The Supreme Court stepped in and ruled 9-0 (which almost never happens) that Trump cannot be removed from the ballot. Their message to the country was clear, let the voters decide Trump's fate, not the court system.