What are their accommodation?

The Word 'their' is a pronoun called a possessive adjective, a Word placed before a noun to describe that noun as belonging to specific persons or things.

The possessive adjective 'their' is a third person, plural pronoun; a Word that takes the place of a plural noun, or two or more nouns, for people or things spoken about.

The Word 'accommodation' is a noun; a Word for a place where people can live, stay, or work; an agreement that allows people or groups to work together; something done to provide what is needed or wanted; a Word for a thing.

The term 'their accommodation' is a noun phrase, a group of Words that can function as a unit in a sentence.

The noun phrase 'their accommodation' is made of of the noun 'accommodation' described by the possessive adjective 'their'.

Examples:

My parents will arrive on Friday. I must prepare their accommodation. (the accommodation of my parents)

The delegates will meet to discuss their accommodation of objectives. (the accommodation of the delegates)