Creating audiences based on interests, location, job title, age, and many other factors is a great tool. This allows you to reach people who aren't yet familiar with your brand but may potentially be interested.
If you're familiar with marketing, you know that a customer who already knows or uses a brand (e.g., by choosing its services or products) is more valuable. That's why remarketing, or reaching people who have already encountered your brand by, for example, visiting your website, is so crucial in this industry.
However, to know whether a person has visited your website, the page must be properly connected to the Meta Ads advertising system. The Meta Pixel enables us to achieve this "connection."
What is the Finish Pixel?
A pixel is a small script—a few lines of code—placed in the website's code, at the end of its "head" section. A pixel is a tracking code that checks whether the person who visited the website has a Facebook, Instagram, or Messenger account that can be linked to them. If they do, they are added to a database of people you can later reach when running ads.
Note: The pixel collects data from the moment it's installed. To create a properly functioning audience of those who visited your website within the last 14 days, for example, the pixel must be active on the website for at least 14 days (the pixel collects data for a maximum of 180 days).
You don't need to be a programmer to use and understand the Pixel. Just install it on your website once and test to make sure everything is working properly.
Pixels are not everything – what are events?
Before you check if the pixel is working properly on your website, learn what events are.
If you already have the basic pixel code installed on your website, you can build remarketing groups and reach people who have visited your page. But what if you want to narrow down that group to audiences who have taken specific actions on your site, like adding a product to your cart or submitting an inquiry on your contact page? That's what events are for.
With the basic pixel code, you can reach people who have visited your website, and with events, you can reach people who have performed specific actions on your website.
Events are installed on specific pages (they are triggered after they are loaded) or elements, e.g. buttons (the event is triggered after the button is pressed).
Example events:

ViewContent
an event most often found on product cards, e.g. related to expanding the description.

AddToCart (add to cart)
an event to install in your shopping cart or "add to cart" buttons. This event will let you know how many people visited/filled your shopping cart.

Purchase
An event that should be included on the "thank you page" after a purchase. This lets you know how many people made a purchase.
You can build audiences based on events. A good example of using them is targeting people who abandoned their shopping cart with an ad (this includes all people from the AddToCart event, excluding those from the Purchase event).
Pixel Helper
If you're a Google Chrome user, you can install the "pixel helper" plugin. It will show you which pixels (and events) are active on specific pages.