Spells

Spells are magical effects. Spells are not always attacks. Some spells heal, buff players, change fate, or charm individuals. Every spell has a level from 0 to 9.
A spell’s level is a general indicator of how powerful the spell is. Spell level do not correlate with a players level. A character has to be at least 17th level, not 9th level,
to cast a 9th level spell. Not all characters can cast every spell. Only certain classes can cast certain spells. The Player's Handbook has a list of all of the spells a class can use.

Spells may require up to three elements: Verbal (V), Somatic (S), and Material (M). This means the spellcaster must either speak a comand, make a hand gesture, or use a special marterial to cast.
Spells take different times to cast. Some will be instantaneous and some take up to an hour. The effects of spells also have different lengths.

Will a character may know many spells, this character can only cast a certain number of spells a day. With different levels come a different number of spell splots. When a player casts a spell, they use up a spell slot.
Spell slots come back after a character takes a short rest.

There are also different schools of magic:

Abjuration - create magical barriers, negate harmful effects, harm trespassers, or banish creatures to other planes

Conjuration - Spells involve the transportation of objects and creatures from one location to another.

Divination - Spells reveal information

Enchantment - Spells affect the minds of others, influencing or controlling their behavior

Evocation - Spells manipulate magical energy to produce a desired effect

Illusion - deceive the senses or minds of others

Necromancy - Spells manipulate the energies of life and death

Transmutation - Spells change the properties of a creature, object, or environment