YouTube improved the filters that from them you can be chosen after searching so that they show also close or complementary subjects or accounts, particularly relevant for search.
The new proposals are called Explore.
The option to change the order of results (relevance, a number of expectations, etc.) placed more prominently.
You can drag any filter to the search box in order to create a custom query or click on it to view only relevant results to the original query.
It is important to note that Explore bids not shown in all searches yet.