Dizziness and vertigo are different things, and the difference is the diagnosis

These two words get used interchangeably, and they describe different
experiences:

Which one you have is worth getting right before you describe it to anyone,
because it points at different causes. Both can worsen when you walk, stand
up or move your head, and both can make you lose your balance. Either may
come with nausea, vomiting, sweating, trouble walking, or ringing in the ears.

Stop here if any of this applies

Get emergency help right away if sudden or severe dizziness or vertigo
comes with:

• Vision problems
• Slurred speech
• Weakness

Those point to something more serious than an inner ear.

What causes them

Both become more common with age — not because ageing causes dizziness
directly, but because older people tend to have more health conditions and
take more medicines, and both raise the chance of it.

• A sudden drop in blood pressure
• Dehydration
• Getting up too quickly
• Certain medicines
• Inner ear problems — Ménière's disease, and **benign paroxysmal
  positional vertigo (BPPV)**, which is the most common cause of vertigo
  there is
• Motion sickness
• Migraines
• A head injury, or ear surgery

Sometimes the dizziness is a symptom of another condition altogether.

Finding the cause, and treating it

Your provider will ask about your medicines and symptoms and may examine you,
often checking hearing, balance and the way you walk. An imaging test follows
only if a stroke or a head injury is suspected.

Dizziness often gets better on its own. If it keeps happening, the
treatment depends on the cause, and may be balance exercises, medicines, or
both. That BPPV — the commonest cause of vertigo — responds to positional
exercises is a good reason to get the cause identified rather than waiting it
out indefinitely.

Source: National Institutes of Health, via MedlinePlus.