I am trying to get my head around this as it doesn't make sense to me at the moment.
We are in 2256 and the Discovery is currently experimenting with a spore drive. During the show it is saying how it can travel vast distances pretty much instantaneously. However, in other series a lot of speed is mentioned as a particular warp speed.
I am struggling to compare the differences. This spore drive seems to indicate that it is the fastest available ever.
In Enterprise, the titular ship Enterprise NX-01 could go at a maximum warp speed of 5.06.
In The Original Series, set after the Discovery timeline, USS Enterprise NCC-1701, could run at a maximum speed of warp 8.
So between this time, during the Discover timeline we have a spore drive which can go at X, beating any current warp speed (around 5), but then this seems to be over when it comes to warp 8.
I am assuming the series will go into this detail later on, maybe the spore drive dies or cannot be used so they go back to warp engines, but for now I can't work out how to compare these speeds that the ships are all going at. I am a rather new Star Trek viewer, I was only old enough when Stargate was showing so that was my original entry into sci-fi!