Spell slots are a mechanic in the game of Warcraft that play a role in the multiclass system. Multiclasses are a mechanic that allows players to choose from different classes, each with their own set of abilities and playstyle. In order to use spell slots, you must first dual class into a warlock. Warlocks have the unique ability to cast spells from both the warlock and priest spellbooks.
Once you have dual classed into a warlock, you can then use your warlock spell slots to cast spells from your priest spellbook. Spell slots work in a similar way to gear, where you can only use certain spells from each spellbook depending on your character level. This means that you cannot use all of your priest’s spells at level 1, but as you level up, you can unlock more priest spells and use them in your warlock spell slots. This allows players to choose which abilities they want to invest in and helps tailor your playstyle to fit your preferred class.