Any tag in HTML can have an id and a class attribute.
You can use those to make JS and CSS to access certain tags, by 3 different main things:
name (tag name)
With name you can target any tags of the same name. You can for example specify every paragraph element <p></p> to be red.
id is an identifier for a tag, not 2 tags can have the same identifier, but you can use it to specify 1 certain element.
class is a group for a tag, similar to id, but same class can be given for multiple individual elements.