As written in the description, it dynamically improves your techlevel based on how much you have researched.

But what is tech level?

the technology level of your faction is a value which impacts research speed.
if you research a technology which is considered to be more advanced (has a higher techlevel) then your faction (= your techlevel), then a penalty is added, making it take longer to research it.

Unfortunately in rimworld 1.1 the research tree doesnt show the techlevels of every project anymore, making it more difficult to notice.

In short though, a better techlevel means faster reaserch. And in vanilla your techlevel is unchangable. If you start as a tribe you will have a massive, permanent research penalty. Tech Advancing allows you to get rid of it by doing research.

Does this work with Tech Block or do they sorta do the same thing?

Should work with techblock, but you can achieve a similar thing with techadvancing by enabling the setting that says something like "make research projects above your technology level X times more expensive".
i would say just play around with it and see if you like techadvancing's way, and if you dont then you can just install techblock in conjunciton with techadvancing

Great thanks!

Any idea why RW 1.1 removed the information on the research project's tech level?

No clue, youd probably have to reach out to the rimworld dev team for that

Where can you see what your current tech level is?

the vanilla techtree used to tell you that. They removed it though. Now you can look it up in the techadvancing menu where it says Resulting techlevel: .... i believe