PPP, or Precise Point Positioning, (the real-time version, though PPP can be a post-processing solution as well) is sort of like WAAS on steroids, providing sub-meter and in some cases a handful of cm accuracy in.
Typically this involves a bunch of ground stations grabbing GNSS signal data, and sending it to processing centers where the data/errors are modelled/computed/crunched. Then the correction info can be sent to end users via the internet or blasted up to satellites and relayed to the end user's receiver via L-Band signals.
I think there may be some free services, but from what I understand most providers of PPP services are subscription based, or similar.
This is what Trimble's CenterPoint RTX service is. They claim 2cm RMS. I'm not sure how long it takes for a solution to converge with that accuracy, but I recall that some systems require (or at least used to require) something like 10 minute occupations to get full accuracy.
All of that said, just from that image I'm not sure if Javad is advertising a Javad PPP service, or simply stating that it has receivers/radios that facilitate the use of other L-Band PPP services.
Interestingly, I believe starting with the Delta-3 receivers, Javad gear has the ability to track and decode the QZSS LEX (L6) signal, which is an L-Band signal containing PPP correction data, among other things.