What is meant by minimum rate of wages under The Minimum Wages Act, 1948? How is it fixed/revised ?

Section 3(1)(a) of the Minimum Wages Act, 1948 lays down that the 'appropriate Government' shall fix the minimum rates of wages, payable to employees employed in an employment specified in Part I and Part II of the Schedule, and in an employment added to either part by notification under Section 27. Further, according to Section 3(2) of the Minimum Wages Act, 1948, the 'appropriate Government' may fix minimum rate of wages for: time work, known as a Minimum Time Rate; piece work, known as a Minimum Piece Rate; a "Guaranteed Time Rate" for those employed in piece work for the purpose of securing to such employees a minimum rate of wages on a time work basis; (This is intended to meet a situation where operation of minimum piece rates fixed by the appropriate Government may result in a worker earning less than the minimum wage); and "Over Time Rate" i.e. minimum rate whether a time rate or a piece rate to apply in substitution for the minimum rate which would otherwise be applicable in respect of overtime work done by employee. Section 3(3) of the Minimum Wages Act, 1948 provides that different minimum rates of wages may be fixed for - different scheduled employments; different classes of work in the same scheduled employments; adults, adolescents, children and apprentices; different localities. Further, minimum rates of wages may be fixed by any one or more of the following wage periods, namely: by the hour, by the day, by the month, or by such other large wage periods as may be prescribed; and where such rates are fixed by the day or by the month, the manner of calculating wages for a month or for a day, as the case may be, may be indicated. Provided that where any wage-periods have been fixed under section 4 of the Payment of Wages Act, 1936, minimum wages shall be fixed in accordance therewith. According to Section 3(1)(b) of the Minimum Wages Act, 1948, the 'appropriate Government' shall review the minimum rates of wages so fixed at such intervals as it may thing fit, such intervals not exceeding five years, and revise the minimum rate of wages, if necessary. This means that minimum wages can be revised earlier than five years also.