Who leads the house of representatives and how is this role different from that of the leader of the senate

The leader of the House is the Speaker of the House. the speaker is a House member who is elected by the other representatives. Although unlikely, it is possible for the Speaker to come from the minority party if the member is well-respected enough to gain votes from the majority. In the Senate, the official leader is the president of the Senate, which is a title held by the vice president of the United States. However, because this role is mostly ceremonial, the true power in the Senate is held by the majority leader

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.