Standard Chinese is used for writing basically anything and everything official when writing in Chinese in countries and places that use Chinese, and is closer to Mandarin than any other Chinese language. Written Cantonese, for example, is not Standard, but is used for some unofficial things in Hong Kong and by Hong Kong people online a lot. I can give you a few examples:
How
Standard: 怎麼（樣）、如何
Cantonese: 點（樣）
This
Standard: 這個, 這+量詞
Cantonese: 呢個，呢+量詞
Example: Standard 我怎麼可以解決這個問題？vs. Cantonese 我點可以解決呢個問題？
Why
Standard: 為甚麼、為何
Cantonese: 點解
That
Standard: 那個
Cantonese: 嗰個
Eat
Standard: 吃
Cantonese: 食
possessive particle
Standard: 的、之
Cantonese: 嘅、啲 (plural), 之
particle marking perfective aspect or continuous state
Standard: 了、著
Cantonese: 咗
Example: Standard 你為甚麼吃了我的蘋果呀？ vs. Cantonese 你點解食咗我嘅蘋果嘅？
How
Standard: 怎麼（樣）、如何
Cantonese: 點（樣）
This
Standard: 這個, 這+量詞
Cantonese: 呢個，呢+量詞
Example: Standard 我怎麼可以解決這個問題？vs. Cantonese 我點可以解決呢個問題？
Why
Standard: 為甚麼、為何
Cantonese: 點解
That
Standard: 那個
Cantonese: 嗰個
Eat
Standard: 吃
Cantonese: 食
possessive particle
Standard: 的、之
Cantonese: 嘅、啲 (plural), 之
particle marking perfective aspect or continuous state
Standard: 了、著
Cantonese: 咗
Example: Standard 你為甚麼吃了我的蘋果呀？ vs. Cantonese 你點解食咗我嘅蘋果嘅？