10 Key Definitions You Should Know When Investing in Online Advertising

Online advertising seems simple: you launch a campaign, set a budget, and wait for results. But behind successful campaigns lies careful planning, testing, and analysis of dozens of metrics.
When the client understands the basic terms, the conversation with the marketing specialist becomes more productive and the decisions – more informed.

In this article, we will look at the 10 most important definitions that every business owner or client should know when starting to work with someone who manages online ads.

1. Impressions

Impressions indicate how many times your ad was shown – regardless of whether someone clicked on it or not.
 Example: if the same ad appears 1,000 times to different users (or even to the same person more than once), that means 1,000 impressions.
Important: many impressions do not necessarily mean success – they indicate visibility, not effectiveness..

2. Clicks and CTR (Click-Through Rate)

CTR is the percentage of people who clicked on your ad out of those who saw it.
Formula
CTR = (Number of Clicks ÷ Impressions) × 100
Example: 100 clicks out of 5,000 impressions = 2% CTR.
Why it matters: A high CTR usually means that your ad is engaging and relevant to your audience. A low CTR could be a sign that your message, image, or audience needs to be adjusted.

3. Conversions

Conversions are the specific actions you want people to take—a purchase, sign up, inquiry, or download.
This is the ultimate goal of your ads.
Important: Not every conversion is a sale—for some businesses, it might be signing up for a newsletter or adding a product to their cart.

4. CPA / CPL (Cost per Action / Cost per Lead)

CPA shows how much each desired action (for example, a purchase or a completed form) costs you.
Example: you spent 200 BGN and received 10 inquiries → CPA = 20 BGN
Why it matters: this is the real performance indicator. It’s not clicks or impressions that are the goal – it’s whether every penny spent leads to an action.

5. ROAS (Return on Ad Spend)

ROAS measures the return on investment in advertising.
Formula
ROAS = (Ad Revenue ÷ Ad Spend)
Example: if you spent 1000 BGN and earned 5000 BGN, ROAS = 5 → that is, 5 BGN for every BGN spent.
Good to know: ROAS is important for online stores and direct sales campaigns, but it is not always applicable to brand campaigns or services with a longer decision cycle.

6. Audience / Targeting

This is the group of people to whom the ads are shown.
It can be defined by age, gender, location, interests, behavior, or even based on previous interactions. Good targeting saves budget because the ad only reaches potentially interested users.
Example: an ad for sports shoes can be targeted to people aged 18–35 who are interested in fitness and marathon running.

7. Remarketing / Retargeting

These are campaigns aimed at people who have already interacted with your business – they visited the site, added a product to the cart, but did not make a purchase.
Example: if you were looking at sneakers and then see them as an ad on Facebook or Google – this is remarketing.
Benefit: it is much cheaper to bring back a user who already knows the brand than to attract a new one.

8. Lookalike Audiences

Meta and Google’s systems can analyse your customers and create audiences of people who have similar behaviours.
Example: if you have a database of customers, the platform will look for people who have the same habits online.
Benefit: this is a powerful tool for expanding the market without losing focus on the right audience.

9. Landing Page

This is the page that the ad leads to.
It should be clear, with a specific message and a clear goal – to direct the visitor to action.
Example: f the ad is for a free consultation, the landing page should contain a request form and brief information, not a long list of services.
Tip: a weak landing page can ruin even the best campaign. A good landing page often decides whether there will be a sale.

10. Pixel

A pixel is a small piece of code that is placed on the site and tracks visitor behavior.
Thanks to it, you can track actions (conversions), create remarketing campaigns and optimise results.
Important: the pixel must be set up correctly - otherwise the data on which the campaigns are optimised will be inaccurate.

How to use these definitions:

You don't need to be a marketing expert to understand the reports, it is enough to know what the indicators mean and what the relationship between them is.

• High CTR but low conversions → the ad attracts attention, but the landing page does not convince people to act.
• Low CTR but high ROAS → the ad reaches the right people, even if only a few.
• High CPA → it’s time to optimise the audience or message.

Conclusion

Knowledge gives confidence.
When the business owner understands the metrics, conversations with the agency or advertising specialist become clearer, decisions are smarter, and results are better.
Online advertising is not magic, but a process in which data leads to success. Knowing these basic terms is not a client’s obligation, but it is a great advantage. When you understand what the metrics mean and how to interpret them, you can make more informed decisions and monitor the real progress of your campaigns.

Understand the value of strategically built advertising and invest in a proven expert who will take over the overall management of your campaigns and make sure they work effectively from day one.