Catch it back!
97% of the people who visit your site do not buy, at least on the first visit.
Most people need to see your products / services multiple times to make up their mind to buy.
Think well about it, you too often before making a purchase, inform yourself, read, look at competing sites, read reviews, go back to the seller's site and re-read several times. Especially if it's the first time you buy that product.
But this does not mean that you are not interested, it just means that you need time to decide.
And what happens if when you decide to buy you no longer find that particular site? It happens that you buy from another.
So site "A" spent money on advertising to get visits, but then people buy from site "B".
The number 1 goal of marketing is not to lose customers who have already visited you. This is called Re-Marketing.
Did you ever notice that after you visited a site, for days you find your advertising wherever you go?
For example that pair of shoes that you searched for on Amazon .. then you found yourself advertising Amazon on that blog you were reading, then on your Facebook while you read the posts and then again in your email box .. and then again in your instagram??
This is because advertising a person who has already shown an interest in your product / service brings sales at a cost of 70-80% lower, just because you already know he is interested, he simply needs time to decide to buy. And when he decides to do it you must absolutely be there, otherwise he will buy from another!
If you have an e-commerce and you do not do remarketing you are losing at least 60% of sales.