Targets and resolving spells

[Keyeto]

Auras and Zur/Bruna don't target

Auras target before they enter the battlefield. That's why bestowing upon heroic creatures is so sweet.

{Zur, the enchanter}
{Bruna, light of allibaster}

Am I wrong? I thought these cards were ways to get around shroud...

They get around shroud. Aura spells target, but the permanents themselves do not. So anything that places them onto the battlefield gets around shroud.

[MtJesus-Johnson]

Auras and Zur/Bruna don't target

Auras target before they enter the battlefield. That's why bestowing upon heroic creatures is so sweet.

I totally misted your post there. You were talking about using Bruna or Zur. I've never heard of Zur before, so that must've thrown me off. Xp

[Pleeb]

Trying to answer the original question:

How do I tell whether a spell targets as its cast or upon resolution? Examples would be ✨spectacular!✨ Thanks!

If the spell says target, you have to choose the targets as they're being cast, and only another game interaction can change them.   When someone gets to "target" something on resolution, they aren't really targeting according to the game mechanics. Usually they are choosing or placing. Some examples of this:
Target player sacrifices a creature. In this example a player is being targeted and upon resolution chooses a legal permanent to sacrifice.
Search your library for a creature and place it into the battlefield. You choose your card as you search your library.

Essentially, if you see the word target, you have to make the decision right away.