This article is meant to introduce you to the concept of a spellcast. It's an important thing for every scripter to know in brief how this works because spells are one of the main "channel of interaction" between objects ingame. Whenever you pick someone's pocket as a rougue, init a trade with other player, use an item or simply hurt someone's ass using magic - a spell is involved. Each spell is indentified by it's spellId entry in spell.dbc. SpellInfo class is a C++ interface to that table (among other related dbc and sql tables). Most of the cast process is handled inside a Spell class representing dynamic state of each cast. Behaviour of that class can be affected using SpellScript class objects. A mechanism with such big impact on everything is complex, so to simplify our view of what's going on it's split into several phases. Ingame, they occur in order same as in this article.
...