Searching by keywords lets you search using one or more words.
For example: "Analyst Programmer"
The "at least one of these words" option implies an OR between each word.
-> search for postings containing: Analyst OR Programmer.
The "all words" option implies an AND between each word.
-> search for postings containing: Analyst AND Programmer.
The "exact search" option means an exact match.
-> search for postings containing the exact phrase: Analyst Programmer.
Punctuation marks such as commas (,) full stop (.) semicolons (;) and colons (:) are ignored.