When someone is holding a speech, their primary goal is to keep their audience engaged. This is why it's important for them to remain focused only on what they are discussing. When too many topics are involved, it becomes difficult for the audience to follow.
When you're unsure about what a word means, you can look it up in a dictionary - an alphabetically arranged listing of words that contains various information about them, such as their definitions, examples, origin, and pronunciation. This is how you can find the correct answer to questions such as this one.
Words that fit the sentence you were given are <em>irrelevant </em>and <em>germane</em>.
When something is irrelevant, it's not related to the discussion or topic.
When something is germane, it is related to the discussion or topic.
