When Senators want to speak in the Senate, they first ask to be "recognized" by the Presiding Officer. The Presiding Officer is another Senator who is presiding over the Senate at that time and maintaining order in the Senate chamber. When the Presiding Officer "recognizes" a Senator, that Senator then has permission to begin speaking.
Usually, Senators speak as though they are talking to the Presiding Officer directly, even if other Senators are present. Senators don't usually interrupt each other when they are speaking. Senators may usually speak for as long as they want while on the Senate floor.
