Thermal Foundation is a mod for Minecraft, which is a base mod for many of the mods in the Thermal Series, such as:
* Thermal Cultivation
* Thermal Dynamics
* Thermal Expansion
* Thermal Innovation
* Thermal Integration
* Thermal Locomotion
And more.
There are also many nonThermal mods, other ones made by CoFH and some by 3rd parties. Some other mods using Thermal Foundation include:

AllTheCompressed
Awesome Sauce Core
ExtraTiC Patches - Universal
Ignition: Foundry
NetherFoundation
Redstone Armory
Redstone Arsenal
Redstone Repository Revolved
Roots
And many more
For players, Thermal dynamics does not do much, but for developers, it can be a useful tool. It requires CoFH to be installed for both players and devs, so developers can also take advantage of many of the features of CoFH.
CoFH is also Thermal Foundation's developers and one of their biggest mods.
There are some issues, though, such as the documentation not always being up to date and some stuff changing, but this is because Thermal Foundation has often been on the cutting edge in the past, being one of the first to do lots of things and ended up setting lots of standards such as how Forge Energy was largely based on Redstone Flux. Some other issues include a restrictive licence and the source code not being fully visible on the CurseForge page requiring extra steps to find it. Another big drawback is being MCForge only officially.

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Thermal Foundation Mod