A web server is the software running on a machine that listens for HTTP requests and answers them, usually by sending back HTML, images, or other files, or by handing the request to something like PHP first. Apache, LiteSpeed, and Nginx are three of the most common ones. They all do the same basic job, but they handle traffic differently, and which one sits under your hosting account affects real-world page speed.
What a web server actually does
When you type a URL into a browser, your computer resolves the domain to an IP address, opens a connection to that server, and sends an HTTP request: something like "GET /index.html". The web server software on that machine is what receives the request, figures out what to do with it, and sends back a response. For a static file, that's often reading the file off disk and streaming it back. For a dynamic page, like a WordPress post, the web server hands the request off to PHP, waits for PHP to generate the HTML, then sends that back to the browser.
Along the way, the web server also handles things like: matching the request URL to the right file or script, applying rewrite rules (the kind of thing you see in an .htaccess file), serving cached copies of pages, enforcing HTTPS, and logging every request. This is also where redirects live, whether that's forcing www or forcing HTTPS.
Apache
Apache HTTP Server is one of the most widely deployed web servers. Its defining trait is the .htaccess file: a per-directory configuration file that lets you set rewrite rules, redirects, and access controls without touching the main server config. That's convenient, but it comes at a cost. Apache checks for an .htaccess file on every relevant request, walking up the directory tree, which adds overhead compared to servers that read configuration once at startup.
Apache's traditional process model (one worker per connection, or a thread per connection depending on the module) also uses more memory per concurrent visitor than newer architectures built around asynchronous I/O.
LiteSpeed
LiteSpeed Web Server is a newer alternative built to be a drop-in replacement for Apache: it reads the same .htaccess syntax and the same rewrite rules, so sites migrate without rewriting their configuration. Under the hood it uses an event-driven architecture instead of Apache's process-per-connection model, which means it handles many simultaneous connections with less memory and CPU per request. It also ships with its own page cache, LSCache, built into the server itself rather than bolted on as a separate plugin layer.
On most WordPress hosting accounts that run on LiteSpeed, WordPress installs get the LiteSpeed Cache plugin pre-configured along with a Redis object cache, so both page output and database query results get cached without extra setup.
Nginx
Nginx takes a different approach: no .htaccess support at all. Every rewrite rule and redirect lives in one central config file, which the server reads once. That's a deliberate trade: less per-request overhead, but no ability for an individual site owner to change server behavior without editing (and reloading) the main configuration. Nginx is also built on an async, event-driven core from the ground up, which is why it's popular as a reverse proxy sitting in front of other servers, in addition to serving sites directly.
Why this matters for your site
You generally don't choose your web server software directly, your host does, and it's usually invisible day to day. Where it shows up is page speed under load and how much a given plan can handle before things slow down. An event-driven server with built-in caching, like LiteSpeed with LSCache, tends to hold up better under traffic spikes than a traditional Apache setup with no server-level cache, because far fewer requests actually have to run PHP and hit the database.
It also explains why the same config file works or doesn't. If you're moving a WordPress site that relies on a custom .htaccess full of redirect rules, LiteSpeed and Apache will both honor it as-is; Nginx will not, and those rules would need to be translated into Nginx's own syntax by whoever manages that server.
When to open a ticket
If a page feels slow and you're not sure whether it's caching, PHP, or the database, that's worth a support ticket rather than guessing. Include the URL and roughly when you noticed it, and support can help narrow down where the slowdown is coming from.