Learn Spanish (Spain): El perro pequeño es para los hombres.

Since there is more than one man, the noun hombre becomes plural (hombres). In Spanish, the word for 'the' must match the noun in both gender and number. So, the singular masculine article el changes to the plural masculine los.

How do we know whether to add -s or -es to make hombres?

To make a noun plural in Spanish, you look at its last letter. Because hombre ends in a vowel (the letter e), you simply add an -s to the end. If the word ended in a consonant, you would add -es instead.

Why is the order perro pequeño instead of pequeño perro?

In Spanish, descriptive words (adjectives) like pequeño almost always come after the noun they describe. So, instead of saying 'the small dog', you literally build the sentence as 'the dog small'.

Why do we use es instead of está in this sentence?

We use es (from the verb ser) because we are talking about who the dog is intended for. When combining 'is' with para (for) to show a recipient, you always use ser, not estar.