A website is checking your browser before it lets you access it to ensure you're not a bad bot that is trying to do malicious things such as a DDOS attack.
The majority of websites now are using a service called Cloudflare that works to stop DDOS attacks that bring websites down.
The Cloudflare service routes traffic through their webs servers and then connects you with the website server after checking to see if you're a bot or a legit user.
If you're a legit real user for the website then the browser check will then load the website after a few seconds.
I've noticed this happening on lots of websites and even this one.
The Cloudflare service helps ensure the website is not attacked by bots and DDOS attacks and ensures the security and uptime of the website.