タマホーム - TamaHome
This was an advertisement for a construction/real estate company. The "ホーム" part is clearly a loanword, but Tama is a section of Tokyo and would normally be written in kanji (多摩市). I think it's written in カタカナ not only to make the company's whole name カタカナ (rather than a mix) and also to highlight the company's modernity/edginess. Their site shows homes which are all of a very modern and bold style, so their choice to write their name in a nontraditional style reflects this.
This came from the ad for the Japanese version of The Incredibles, seen above. It is a loanword from English, and I think it was used here to establish a connection between the English and Japanese versions of the movie. There is a Japanese word for 'incredible,' but this emphasizes that they are the same movie.
I think textbooks explain katakana in different ways because it is such a broad topic that there isn't a "best" way to teach it. Our textbook first introduced it for its use in loanwords, which I think is a good approach because that is where a beginner will see katakana most often. Words like アメリカ and コーヒー are very good words to know when beginning Japanese, whereas onomatopoeia is a much more complicated topic that wouldn't concern most beginners.
