A standard AB-Solution installation blocks HTTP ads, meaning they were served from a Web-server running the HTTP protocol.
It may leave gaps in the web page where the blocked ad would show.
Nowadays, more and more (advertisement) servers run on the secure protocol, HTTPS, the one with the green lock pad in the URL bar.
The AB-Solution website runs on both versions, you likely see the green lock shown here.
The pixelserv-tls addon adds the capability to block these HTTPS ads as well.
And not only that, it fills the space left by blocked content with a pixel-sized image, hence the pixelserv name. The -tls stands for Transport Layer Security, HTTPS is the protocol name for it.
Last update on 2017-02-28 by thelonelycoder.