Gad, Reikh and Datta Blocks- Block Printing

While looking for the definition of gad, rekh and datta blocks, I came across the following in website of Indianetzone" The gad, rekh and datta are three types of blocks that are distinguishable by their different styles of carving. The gad is carved in intaglio and is engaged to print large background figures, while rekh and datta are carved in complete relief. Rekh blocks also mark the outlines of the motif and are often used in conjunction with gad blocks, the rekh then forming the fine elaborate lines within the impression made by the gad block. Datta is carved in bold relief and complements the designs of both the gad and rekh blocks. Each of these blocks is used separately or together to produce endless design variations."

Now some terms were not clear to me. For example what is "....carved in intaglio.." means, on searching I found this website of carving patterns giving a beautiful definition and explanation, basically carving intaglio is "Intaglio carving uses the reverse technique to produce the image effect. Here, the main image is the negative areas of the work, instead of the background being carved away it is the design the you remove."

And what is " carved in.. relief" ? For this Wikipedia came to rescue: "Relief carving can be described as "carving pictures in wood". The process of relief carving involves removing wood from a flat wood panel in such a way that an object appears to rise out of the wood"