Reading is a mechanism by which a bill is introduced to, and approved by, a legislature.

Second reading
A second reading is the stage of the legislative process where a draft of a bill is read a second time. In most Westminster systems, a vote is taken in the general outlines of the bill before being sent to committee.
In Canada, second reading occurs in Parliament. Members debate and vote on the principle of the bill. The House may decide to refer the bill to a legislative, standing or special committee, or to a Committee of the Whole for consideration (clause-by-clause study of the bill). The Committee may summon witnesses and experts to provide it with information and help in improving the bill. The committee then reports the bill to the House clearly indicating any amendments proposed. The house then considers amendments, voting for or against them.
In the U.S. practice as followed in both the Congress and the state legislatures, the second reading occurs after the bill has been vetted by committee and includes debate on amendments to the bill. If the bill is passed identically on second reading by both houses of the legislature, no further action is necessary.
In Ireland it is referred to as Second Stage, though the motion at second stage is still "that the Bill be read a second time", as in some other Westminister systems. A bill introduced in one house enters the other house at Second Stage. Once the bill passes second stage it is referred to a Select Committee of that house or taken in Committee Stage by the whole house.
The different roles of the second reading are in part a reflection of the different powers of legislative committees. Legislative committees are far more powerful in the United States than in Westminster systems.