Answer:
Complex sentence
Step-by-step explanation:
A complex sentence is a sentence made up of an independent clause (one that expresses a complete thought) and a dependent clause (one that can not stand alone as a sentence because it does not express a complete idea). In this type of sentence, the dependent clause is often introduced by a coordinating conjunction such as while (like in the sentence), after, because, since, if, although and until.
While the others went swimming, we made a sand castle is an example of this type of sentence because it has a dependent clause: While the others went swimming and an independent clause we made a sand castle.