Usage of Lego web-components
A web-component can optionally have 3 parts: some HTML in a <template> tag, some JavaScript in a <script> tag and some CSS in a <style> tag.
You can make a web-component for muliple reasons.
If you just want to re-use a piece of HTML, the <template> tag is all you need.
If you want to polish it’s look 💅, <style> is your friend. Bonus: it’s fully scoped with no leaking out of context.
When some user interaction or reactiveness is demanded, <script> is going to be the guy.