Some of my readers might not be clear on what I mean when I use the terms "Taiwanese" and "Chinese" to refer to both language and nationality. Indeed, the meaning of these words can be somewhat ambiguous and also depend on the political views of the person using them. So to eliminate any further confusion in my blog posts, here's what I mean:
When indicating nationality, "Taiwanese" refers to people from the island of Taiwan. Now, anyone who's followed anything about East Asian current events in the last ten years knows that some consider Taiwan a renegade province of mainland China. In fact, Taiwan is sometimes referred to as the Republic of China, as opposed to The People's Republic of China. Taiwanese who are pro-independence (including this author) do not consider themselves "Chinese"; others, however, do. When I speak of Taiwanese, I mean people who live on or are from the island of Taiwan; when I speak of Chinese, I mean people who live on or are from mainland China.
The political situation is confusing enough; let's consider now the distinction between the Taiwanese and Chinese languages. The term "Chinese" as it refers to language is actually very ambiguous and should probably be avoided (see a detailed Wikipedia treatment here). It's a subject for linguistic debate whether Taiwanese and Cantonese (which is spoken in Hong Kong) are their own languages or a dialect of Chinese. When I speak of Chinese, I am referring to Mandarin, which is spoken far more widely than either of the two languages mentioned above. Spoken Taiwanese is completely different in sound than Mandarin, as is spoken Cantonese, although the written forms are all the same. However, the official language of Taiwan has been Mandarin for several decades, and most younger Taiwanese speak Mandarin preferentially; the use of Taiwanese is more common in rural areas and among older people.
Because my parents' first language is Taiwanese (though they speak fluent Mandarin), it's what they use at home and therefore what I learned. I'm very proud that I speak Taiwanese, but it's much more practical to know Mandarin. In time, I hope to have the best of both worlds by being fluent in both.