More accurately, the IceCube Neutrino Observatory is a series of strings of optical sensors embedded in the Antarctic ice. They detect Cherenkov light emitted by super-high energy neutrinos that pass through the ice.
There are many other neutrino detectors that are much smaller, but those are designed for detecting lower energy neutrinos from the sun or nuclear reactors. IceCube was designed for extragalactic neutrinos with much, much higher energies which required making it so large.
Neutrinos can interact with matter via the weak force, which is so weak and short ranged that most neutrinos incident on matter just pass through it. However, you can imagine if a HUGE chunk of neutrinos falls on matter, at least a few are bound to interact, statistically speaking. These interactions are like collisions, and the collision may result in generation of new particles. If these new particles are energetic enough, they emit a special type of radiation, which can be detected through sensors. So, you're not directly capturing neutrinos, but are making the inference that they are there, because you know a weak force interaction has taken place if your sensor goes off. And to make sure something like cosmic radiation doesn't affect detection, this particular detector is isolated under a huge sheet of ice in Antarctica.
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The first ever neutrino image of the Milky Way galaxy captured by the IceCube Neutrino Observatory
Two big announcements about neutrinos and gravitational waves on the same day
IceCube and NANOGrav will be making announcements tomorrow, July 29th....