Correct spelling, explanation: the noun sheep can be either singular (one sheep) or plural (a flock of sheep). It all depends on context. In this case, we don’t add the suffix to the root in order to make a plural form. This word is an exception in the English language, so we have to be careful not to make a mistake. Sheeps isn’t the right spelling, but sheep indeed is. Always keep that in mind.

Definition of sheep:
noun, plural, our-legged farm animals with a thick, wooly coat
I adopted a dog, so it can protect my sheep from danger.
My sheep always follow each other.

Collocations with sheep:
Some most commonly used collocations include: to farm sheep, to keep sheep, to raise sheep, to rear sheep.
My grandfather raises sheep in Wales.
When you own a flock of sheep, you need to raise and breed them.

Incorrect spelling, explanation: we should be careful when forming plural nouns in English. The fact is that most of them are formed in a simple, regular way: by adding the ending -s or -es to the root, but it’s not always the case. Sometimes the plural’s construction is the same as the singular’s construction, as in the noun sheep. It’s really important to keep this in mind. Sheeps doesn’t exist in any dictionary.