A compound subject refers to a sentence that talks about two or more subjects. The two subjects are combined with a conjunction such as (and, or, neither).
By forming a compound subject the two sentences:"snowshoeing is a popular activity in grand lake. snowmobiling is also a popular activity in grand lake" can be combined into one sentence as follows:
"Snowshoeing and snowmobiling are popular activities in grand land"
This new sentence now contains a compound subject (both snowshoeing and snowmobiling) which is separated by the conjunction "and".
