To follow up on what Linen said, the we reason we don't use the term shock here anymore is to distinguish between the "shock process" or SLAM (Shock Level and Maintain) and various chlorine "shock products" on the market. The simple truth is when it comes to the product side, any chlorine chemical can be sold as "shock" although usually those sold as shock are in a form that dissolves faster (powder vs stick). It also lets the pool stores sell 2 pails of stuff instead of 1. Go look at the fine print label of pail of unstabilized pool chlorine and one of pool shock, chances are both are going to be Cal-Hypo, which is the most common dry chlorine product due to pricing the last couple of years. Shock could also be dichlor, lithium hypo, liquid sodium hypo, or even granular trichlor, although the last is uncommon.
Ike