A keyword is a search term. In other words, you choose keywords based on what you think people will search for.
For example, if your A niche is a topic or subject. Typically a niche is a broad topic like Gaming. However, in the CPA world if you make gaming content, you may be someone that would tackle keywords like "clash of clans hack", which would in turn be your "niche".... More is Clash of Clans you would choose a keyword like “clash of clans hack” because you want to rank for this keyword since you know it will gain you some A lead or conversion is when a visitor follows through with the offer they are presented with. For example, when someone finds your content and clicks on an offer and completes it. You get a conversion thus earning you money.... More!