The keyword(s) used will mainly identify the type of output for which specific text blocks are intended or assist with identifying or distinguishing between text blocks.
In most instances the content of a text block is described by its title and the context in which it appears within the CV/profile. However, keywords are useful in cases where there is no title or where the same title is used within the same context for different outputs or to identify content for different outputs.
See also: Overview: Working with keywords in Researcher Profiles and Keywords field?