Keyword list search when used with wildcard can be confusing because * can mean contain when searching a column but with a keyword search it means a wildcard.
Keyword Search Without Wildcards
To start, Keyword search does not need any operators. Operators are * (Contains), !* (Not Contain), < (Less than), > (Greater than), etc. The search will look for that value that you enter. In the list view, you are using keywords search if the search says "for text" or "Keyword". If you look at image1, "for text" is a keyword search. It will search any term entered and it will look at anywhere on the form that term exists. This type of search is similar to an exact match search.
Keyword search with no wildcard [ abcde ] - will look for that search term only. So If I look for abcde it will bring back records with that term only.
Keyword Search With Wildcards
Keyword search with wildcards acts a little different and will have more results because it will look at the term plus anything before or after the term. It depends where you put the wildcard. Where this differs from just using a keyword is that just using a keyword only brings up that term.
Keyword search with one wildcard [ abcde* ] - will look for the term plus anything after. Will bring back results abcde9, abcde78, abcdenhtg
Keyword search with 2 wildcards [ *abcde* ] - will look for the term plus anything before and after. Will bring back results abcde9, abcde78, abcdenhtg, abcde, uytabcdepoi, 99abcde99
Using a wildcard before and after the search term is the closest type of search to a contains search. Because it looks for the term and it does not care what is before or after the term.
If you look at image1 you will see other search options other than "Keyword" or "for text" search. For example, "Number", "Short Description", "Priority", "Caller", etc. These search options are actual fields on the form and columns on the list view. These search options will use operators in their query. For example, if I choose "Number" option type *0000002 in the search bar on the header of a list it will search for a "Number" that contains 0000002. Refer to image3.
Another characteristic of Keyword search is that it is not a column on a list or field on the form. It is merely a search option that looks for terms on a form. If you look at any list view and click on the condition builder (hourglass looking element) and choose keyword as your query option you will see that no operator is an option other than "are". Please refer to image2.