1.xpath select element
/ means direct child node
//all child nodes
//div[@id='hello']/../p Find element by parent node
//div[@style] div with style attribute
//div[last()] last div element
//div[position()<=2] The first two div elements
//p[@id='ui']/preceding-sibling::div Select all div elements before sibling nodes
// p[@id='ui']/following-sibling::div selects all div elements after sibling nodes
2.css select element
> means direct child node
div p means all p under the div
hello>p,div all p and all divs
div+p sibling node, next to p under div
div~p all p under the sibling node div
div[@style] all divs with style attribute
div: the first div in the nth-of-type(1) element
div: nth-of-child(1) the first of all elements in the child element