In Blokada you can select a third-party DNS provider.
To understand how DNS works, please check this article.
Which content can be blocked?
Some DNS services also provide the possibility to block specific content. The content blocked varies. There are DNS servers that only block ads and tracking. There are servers that specialized on keeping the browsing experience family-friendly. And there are servers that shall protect you from malware. These are only examples and of course there are servers that combine the different types of content. You will have to search for the one that fits your needs best. Reading the description of the DNSs in-app can be a good start.
How do DNS servers block content?
The DNS server filters your DNS requests. If the request should not be blocked it gives back the correct IP. If the request should be blocked it gives back a wrong IP. This IP won’t load the content, but will generate an error or will inform you that the content was blocked by your DNS.
What are the downsides?
The DNS provider decides which content should be blocked. You can’t influence this. If you want to visit a side that the DNS blocks you have to pause Blokada or select a different DNS temporarily.
What are the upsides?
A DNS server can store way more domains than your RAM can. So you might get an increased protection.