Question

Let's play outside is a type of sentence​

Answer 1

Answer:No. Grammarians and linguists have a variety of explanations for this type of first-person imperative construction—sometimes called the let-imperative.

Your best bet is to avoid analyzing let’s as some form of a verb plus the pronoun us. Rather, consider let’s an idiomatic marker of a cohortative first person imperative.

Compare your let-imperative Let’s play outside to a regular first-person imperative where let means “allow” and you is the understood subject: Let us play outside.

Explanation:

Answer 2

It is an Imperative Sentence

Explanation:

Imperative sentence is a sentence used to give command, advice, request, instruction, etc. The object in imperative sentences is usually assumed to be the pronoun ‘you’. ‘Let'  can be used for expressing ‘Proposal’, ‘Suggestion’, ‘Request’, ‘Order’, ‘Wish’, etc.

Examples

Let's go to the mountains for relaxation.

Let her come in.