I'm fairly new to DnD. I'm creating my first wizard and I've been wondering about the Expeditious Retreat spell.
The PHB says:
This spell allows you to move at an incredible pace. When you cast this spell, and then as a bonus action on each of your turns until the spell ends, you can take the Dash action.
Concerning the Dash action, the PHB says:
When you take the Dash action, you gain extra movement for the current turn. The increase equals your speed, after applying any modifiers.
My normal speed is 30 feet. So normally, during my turn in combat, I can move up to 30 feet and take one action (in any order, even splitting my movement up by moving 15 feet, taking an action, and moving another 15 feet, etc). Do I understand correctly that when I cast this spell and as long as it is active, I can essentially move up to 60 feet and take one action during my turn? That is, could the description of this spell be more simply (but equivalently) expressed as:
Your speed is doubled for the duration of this spell.
And if not, what would be the difference?
No, you can't simplify Expeditious Retreat that much. The difference is, Expeditious Retreat requires a bonus action to cast, and only gives you the ability to Dash as a bonus action.
So, in practical terms:
There's a lot more differences between Expeditious Retreat and the simplified version you propose, but I tried to restrict myself to ones that are relevant to you.