Joomla had two search components. Smart Search (com_finder) is part of Joomla 3 and 4, the older Search component (com_search) is part of Joomla 3 and can be installed as an extra component into Joomla 4. Smart Search uses a search index which needs updates while the Search component performs a raw database search without the need for an extra index. This is simpler but the search index has some performance benefits for running a search. With Event Gallery you can use both search components.
The search will return only public visible result. Event/image which are protected with user groups or a password will not appear in the search results.