Guarda l'altro lato.

Here guarda is most naturally the tu imperative of guardare, so it means an informal singular command: look.

A useful thing to know is that guarda can also be the present tense form meaning he/she looks or you look in the formal sense only in some contexts? No—formal you would normally be guarda only as an indicative with Lei guarda, not as a command. In this short sentence, with no subject written and a direct tone, the most likely reading is clearly a command.

Because Italian usually leaves out subject pronouns when they are already clear from the verb form or from context.

So instead of saying Tu guarda l'altro lato, Italian normally just says:

• Guarda l'altro lato.

Adding tu would usually give extra emphasis, contrast, or impatience.

Because guardare normally takes a direct object in Italian.

English says:

• look at the other side

Italian says:

• guardare l'altro lato

So this is very normal. The same pattern appears in:

• Guarda il cielo = Look at the sky
• Guardami = Look at me

This is a very common difference between English and Italian.

Because the definite article changes before a vowel.

Since altro begins with a-, Italian uses l' instead of il:

• l'altro lato

This apostrophe is required here.

A good comparison is:

• il libro
• l'altro libro

The article is placed before altro, and because altro starts with a vowel, the article becomes l'.

Many Italian adjectives do come after the noun, but altro is one of the very common adjectives that normally comes before it.

So Italian says:

• l'altro lato
• un'altra volta
• altre persone

Putting altro after the noun would sound unnatural in this sentence.

So this is a case where English and Italian happen to match well: the other side = l'altro lato.

You can tell from altro.

Here:

• altro = masculine singular
• altra = feminine singular
• altri = masculine plural
• altre = feminine plural

So l'altro lato must be masculine singular.

Compare:

• l'altro lato = masculine singular
• l'altra mano = feminine singular

Even though l' can be used before both masculine and feminine singular nouns starting with a vowel, the form of the adjective tells you the gender here.

It is informal singular, used with tu.

If you wanted the formal singular command, you would say:

• Guardi l'altro lato.

If you wanted to speak to more than one person, you would say:

• Guardate l'altro lato.

So guarda is the form you would use with one person you address informally.

Yes. Guardare can mean both to look at and to watch, depending on context.

For example:

• Guardo la TV = I watch TV
• Guarda me = Look at me

In Guarda l'altro lato, the natural idea is look at the other side, not watch the other side, because lato fits better with looking at something rather than watching an event.

Sometimes yes, but not always.

• lato usually means side in a more concrete or clearly defined sense
• parte is more general and can mean part or side

So l'altro lato is a very direct match for the other side.
In some contexts, l'altra parte could work, but it may sound slightly different in nuance.

For a learner, the safest choice here is to keep:

• Guarda l'altro lato.

No. That changes the meaning.

• Guarda l'altro lato = Look at the other side
• Guarda dall'altro lato = Look from the other side

That little word da changes the relationship completely. Without da, l'altro lato is the thing being looked at. With da, it becomes the position or direction you are looking from.

So the original sentence is correct for look at the other side.