HTML/CSS
This is what a web page is made of. Using these tools, you can compose well designed pages with rich content in it. Web technology is all about compiling HTML and CSS (and some Javascript) and sending it to your browser.
HTML is a markup language, which means it's a syntax for marking up content. For example, this text is in a paragraph HTML element, which looks like this: <p>Hello this is a paragraph element, often referred to as a "p tag"</p>. You can see the opening and closing tags, which specify the type of element, and the content in between.
HTML 5 is the current version of HTML and defines the set of tags available to use. There's not too many, and they're semantically named so it won't take long to learn them. https://developer.mozilla.org/en-US/docs/Web/HTML/Element
Right click on a page and inspect element to see what HTML is being used, and the CSS styles applied to it.
Javascript
Javascript makes pages dynamic and interactive. The actions that are made when you click a button, or loading fresh content in a news feed are created with Javascript.
Server/Network/Browser
This is the ecosystem we operate in. As you create more advanced systems, you will learn about how these pieces work under the hood.
Server scripting
Logic for storing, retrieving, and rendering content. The code on the server looks at the incoming request (the URL you went to) and pulls the right content from the database, and renders it through templates that define where the content goes in the HTML. Some scripting is transactional, like an eCommerce purchase.
Frameworks
Coding kits to help you create sites and applications faster and with better structure. These are collections of code, often open source, which people work on to solve common problems. For example, this site is using Drupal, a CMS to write and display the content. You should learn to use individual tools, but look for frameworks that may fill more advanced needs. Talk to experienced developers doing similar things about what systems they recommend.