So for example, if your domain name is pokerdude.com and you start talking about tennis on your site, then surely you will confuse your customers.
When starting a new website, think carefully where you want to take it before registering a domain name. Your domain name can be generic without keywords in it, and then you build the brand over time.
If you do put keywords in your domain name, then stick with that topic on your site.
Thanks RBJ, good day to you!