Wizard Spellcasting?

[Okamigekido]

So, recently the PC's have leveled up (4 levels) and I'm trying to understand how a wizards spellcasting works. See, this wizard is a necromancer-but as one of her spells, she had chromatic orb?
Can a necromancer wizard ONLY use the necromancy spells, or can she use the ones outside of that? Can someone VERY simply explain to me how this works? (I want to make sure to get it right)

[Bohandas]

They can use some non-necromancy spells, but 1-3 of the other schools of magic (depending on the edition of the game) are unavailable to them

[Okamigekido]

The edition is 5e. If they were to use the non-necromancer spells, can you thing of like,,,a condition in which they would use it? And so this means she should only be choosing from the necromancer spell-list?

[Millstone85]

The edition is 5e.

Then the necromancer can use spells of any school. She is just really good with the necromancy ones.

[Anymage]

This would probably be better in the 5e section. I'll flag this so a mod can do that for you.

In second and third edition, being a specialist meant giving up access to certain schools in order to be better with your chosen school. In second those choices were made for you, in third you got to pick what schools to give up. That's not really relevant to 5e, it's just to explain where the idea came from. The generalist mage who could cast all spells but wasn't particularly noteworthy at any of them was also an option.

In 5e, your specialization is your subclass. There is no generalist subclass that I'm aware of, so that isn't anybody's shtick anymore. Any wizard could potentially learn and cast all of the wizard spells, although in practice you'd run into troubles with money, time, and spell access. You're better at learning spells of your specialization, and often better at using them, but you don't give anything up for them.

Edit: I don't know if it's good form for me to flag this on your behalf. You can flag your own post and ask to be moved to the 5e section no problem, though.

[Anonymouswizard]

Can a necromancer wizard ONLY use the necromancy spells, or can she use the ones outside of that? Can someone VERY simply explain to me how this works? (I want to make sure to get it right)

It very much depends on the system.

The edition is 5e.

5e what? The difference in picking spells on Ars Magica 5e and D&D 5e is massive.

Okay, enough messing around from me.

In D&D 5e a wizards can learn any spells they are of a level to cast when they level up, and when using the PhB subclasses arguably hey a minor benefit from choosing spells from outside their school (mostly balanced by their Subclass features only or mainly utilising spells of that school). Due to the wizard spell list having been cut down compared to 2e/3.X this is important, the wizard is now short on some schools, particularly Abjuration.

Honestly I would have loved to see wizards more focused, maybe specialise Sorcerers in Conjuration and Evocation, Wizards in Illusion, Enchantment, and Transmutation, and Clerics around Abjuration, Divination, and Necromancy, but the game's not designed that way. Limiting a wizard's access to their nonspecialised schools would mess with the balance of the game.