What are the flags beside the US flag at Trump's inauguration (marked by an arrow in the picture below)?
It's the Betsy Ross flag.
The first documented usage of this flag was in 1792. The flag features 13 stars to represent the original 13 colonies with the stars arranged in a circle.
It is the early version of the American flag. Check the below image for more info. Note on extreme left and extreme right doesn't seem to refer to flags.
The existing answers cover the third (lowest) arrow in your image.
The banners marked by the other two arrows are not flags, but bunting (from wiktionary: "strips of material used as festive decoration, especially in the colours of the national flag"). They serve a strictly decorative purpose.
Red, white, and blue bunting is naturally appropriate at an event like an inauguration, but it's also used on other occasions (maybe moreso in former times, when open patriotism was more common, but it's still found at sporting events, particularly baseball). Bunting doesn't need to be accorded the same kind of respect as an actual flag, and there are no rules for its display.