/*Looking inside - Selects all the li elements placed (anywhere) inside the ul;Descendant selector */
ul li

/*Looking inside - Selects only the direct li elements of ul; i.e. it will only select direct children li of ul; Child Selector or Child combinator selector*/
ul > li

/* Looking outside - Selects the ul immediately following the ul; It is not looking inside, but looking outside for the immediately following element; Adjacent Sibling Selector */
ul + ul

/* Looking outside - Selects all the ul which follows the ul doesn't matter where it is, but both ul should be having the same parent; General Sibling Selector */
ul ~ ul

/* selects any <span> that is inside a <p>, which is inside an <article>  */
article p span { ... }

/* selects any <p> that comes directly after a <ul>, which comes directly after an <h1>  */
h1 + ul + p { ... }