Section 1 is a vesting clause that bestows federal legislative power exclusively to Congress. Similar clauses are found in Article II, which confers executive power upon the president alone, and Article III, which grants judicial power solely to the federal judiciary.
Section 2 of Article One addresses the House of Representatives, establishing that members of the House are elected every two years, with congressional seats apportioned to the states on the basis of population.
Section 4 also requires Congress to assemble at least once per year. Section 5 lays out various rules for both houses of Congress and grants the House of Representatives and the Senate the power to judge their own elections, determine the qualifications of their own members, and punish or expel their own members.