Short answer: Alt + Ctrl + A
When you create a new Indesign document and you see this:
I’m not 100% on this, but what I think it is is a layout grid for Asian languages (Chinese/Japanese/Korean) where the space between characters is always the same, you don’t have to worry about kerning as you do in English. In the Chinese version it’s called 版面网格 băn miàn wăng gé.
To hide it go to the View menu (视图 shì tú) > Grids & Guides (网格和参考线 wăng gé hé cān kăo xiàn) > hide layout grid (隐藏版面网格 yĭn cáng băn miàn wăng gé).