When people say "keyword", people usually mean money keywords. However, many SEOs also consider other keyword types to be very important.
These are the keywords that people want rank for. It usually is a keyword that is popular and often searched for.
"espresso machine" would be a Money Keyword for nespresso.com
"buy iPhone" could be a Money Keyword for an iPhone shop
"smartphone accessories" would be a Money Keyword for apple.com
These keywords contain something that can be associated with you or your company. That can be a certain product, service or the company name / domain name itself.
"iPhone", "apple products", "apple.com" and "steve jobs" would be Brand Keywords for apple.com
"CEMPER.COM", "Christoph C. Cemper" and "CEMPER" would be Brand Keywords for LinkResearchTools.com
A Brand Keyword for apple.com could be Money Keywords for you.
"apple products" would be a Money Keyword for a mobile shop
Links are always Brand Keywords. We do that automatically for you.
"http://www.swatch.com/at_de/specials.html" will be assigned as Brand Keyword for www.swatch.com and swatch.com
Compound keywords are keywords that are partly "Brand", partly "Money" keyword.
"smartphone accessories at apple.com" would be a Compound Keyword for apple.com, because it includes both a money keyword ("smartphone accessories") as well as a brand keyword ("apple.com").
"apple smartphone accessories" would be a Money Keyword for a mobile shop
All keywords that don't fit in the above categories are Other Keywords and without any association to you or your company.
"click me", "great site", "link" and images with no alt-text are good examples for Other Keywords
"products" would be an Other Keyword for an online shop.