Searching for content that contains or references all of your search terms. When looking for summer fruit arrangements, you type: Summer Fruit Arrangement and get images that contain all three terms. Picturepark translates your search into Summer AND Fruit AND Arrangement. So the AND operator is added among all your search terms. You can find the translated search query highlighted in bold at the top of the Content Browser.
The "Simple All"-mode is the default search behavior, and it only allows searching for all terms. Picturepark escapes any special characters and symbols. That means there is no particular function for + - |. Picturepark searches for everything you insert, including reserved characters from the underlying search engine ElasticSearch and Boolean operators that are known to have a particular function (+ for AND, - for Exclusion).
That means you probably find nothing, as usually characters + and ? are not used in the metadata.