VAT means Value Added Tax. It is tax specific to EU countries (although also other countries can apply similar tax). For more details see the General overview on EU pages.

Because the SPLOT and WEBPlotter software have origin in EU, they subject to VAT.

For customers outside EU this VAT matter is irrelevant (so they always pay the price without VAT).

This is additonal security code required for remote card transactions (where the card is not physically present). For MC and VISA cards this code is located on the reverse side of the card in the signature strip (last 3 digits here). For more details please see here.