In Salesforce, back-end development is Apex. You write logic like triggers, and Salesforce executes it on the server.
Front-end development is what the user sees - buttons, pages, forms. Most of that code runs in the browser, not on the Salesforce server. This is why front-end is a completely separate discipline. Some developers specialize only in front-end and don't know much back-end at all.
Because front-end is so different from Apex, you're starting from zero regardless of your Apex level. Everything we cover here works even without any Apex knowledge.
Salesforce has three front-end frameworks. From oldest to newest:
Visualforce - the oldest. Getting obsolete, but still has some niche use cases like PDF generation. In 6 years of Salesforce work, I've used it maybe 10 times.
Aura - not absolutely useless, but close. I touched Aura once in 6 years. Once.
LWC (Lightning Web Components) - the newest and by far the most important. I use it almost every week. If you need to build something new in Salesforce, 99% of the time it's going to be LWC.
Don't bother with Visualforce or Aura before learning LWC. Just focus on LWC.
LWC stands for Lightning Web Components. Lightning is just Salesforce's branding. Web means it runs in the browser. Components means… well, you’ll get it later. Everything is a component in LWC!
LWC is built on three web technologies: HTML, CSS, and JavaScript.
HTML defines the structure of a page - where text goes, where elements are placed. It's a markup language, not a programming language. You're not executing logic, just describing layout.
CSS handles the visual side - colors, spacing, fonts, how things look.
JavaScript makes things interactive - handling clicks, fetching data, responding to user input.
We start with HTML and CSS, then move to JavaScript.