TAS is True AIR Speed. IAS is Indicated AIR Speed. They both indicate how fast the air is flowing over your wings. And it's that flow that you need to go flying. Whether it comes from the propeller pulling you forward through still air, or the wind blowing over your wings at the start of the take-off run doesn't matter.
The difference between IAS and TAS is a complex calculation that has to do with air not being the same density everywhere. But both are speeds relative to the surrounding air and have no relation to the ground whatsoever. And at low altitudes and at temperate temperatures, IAS and TAS are, practically speaking, the same anyway.
You seem to be confusing TAS and IAS with groundspeed, which is the speed you actually make over the ground.
All performance calculations, including stall speed, are indicated as air speeds. Most of the IAS, some of them TAS. You cannot fly at speeds slower than stall speed (at least not for long) but it's perfectly possible to fly at negative ground speeds.
Groundspeed is relevant for two things only. It's required to know your groundspeed (which you get once you apply a wind correction to your IAS or TAS) so you know when you will make it to your destination - if you can make it there at all. And groundspeed is relevant for landings and take-offs, since the runway will not move with the wind. So we need to fly the aircraft so that it does the wind correction for us.