Bootstrap: is not just a style sheet (that style mainly class names i imagine), it contains UI components, a grid system, adds custom html tags, js plugins for interactive features like tooltips, modals and carousels.

ya entendi, the js in bootstrap is for classes that need js to interact with, like drowdown menus and buttons. The way you mainly use is declaratively is by adding class names to html elements.
another way is programmatically
similar to certain styles are applied to named classes, bootstrap uses the data-* attribute (specifically the data-target and data-toogle)

<button class="btn btn-primary" data-toggle="modal" data-target="#myModal">
Open Modal
<!-- JavaScript to activate a modal programmatically --> 

using that example, #mymodal could as well have been a div with the mymodal id att that gets faded in. in the example it se

so Bootstrap is like a tailwind in the sense that you use it mainly declaratively, by adding class names, but they differ in the sense that Bootstrap also adds javascript to add reactivity to certain elements (like elements with the dropdown class for instance) and Tailwind is just purely css.