what are the other properties like hover ,check ...

Question

we can use hover of and element and cheked of a check box to create dropdown .
ex1 :-

div#child{
display:none;
}
div#main:hover ~ div#child{
display:block;
}
ex2:-
div#child{
transform:translateX(-100%);
div#check:checked ~ div#child{
transform:translateX(0%);
}

/* where check is id of input type checkbox */

similarly what are the other property in web to create dropdown.

are these related to that:-

click of button
check of radio

Answer 1

when you say dropdown, i believe you are referring to <select> tag

https://www.w3schools.com/tags/tag_select.asp

Answer 2

no it is about sidebar or navbar in website