Heatsink paste, looks to be standard white heatsink paste.

Estimated 1 gram per tube(isn't marked on the syringe) - this should be enough to do at least 1 CPUs. CPUs etc can vary in size, but most are pretty small.

In a small syringe, so is easy to apply & you should be able to store the rest for some time, after using some of it. Some heatsink paste just comes in a small bag(you snip the corner off), which means you probably wouldn't be able to easily store any remaining paste.

Heatsink paste is used to allow the heat to transfer from the CPU(or another device) to a heat sink. Most CPUs require this, when adding or changing heatsinks.

Specifications on syringe:
Thermal conductivity: >1.22W/m.k
Thermal resistance: <0.201 degrees celsius-in(squared)/w

Made in Taiwan