Other comments mentioned deuterium and tritium, but didn't mention why those are used, which is also interesting. Plain old hydrogen is really, really, really difficult to fuse. Plain hydrogen nuclei are just single protons. When you squish two of them together, you get helium-2, which is unstable and immediately decays. It can either decay back into two protons, or it can decay into deuterium, which is a proton and a neutron, by emitting a beta particle which converts one of the protons to a neutron.

The second reaction is really unlikely, so the helium-2 almost always decays back into hydrogens. That means that pure hydrogen fuses extremely slowly. That works out in, for example, the Sun, where tremendous heat and pressure is maintained for billions of years. It doesn't work so well in a bomb which can only maintain fusion-level temperatures and pressures for tiny fraction of a second.

Thus, fusion bombs always use deuterium or tritium. Practical bomb designs typically don't use those directly (hydrogen is a pain to work with), but rather use lithium turns into deuterium or tritium in the neutron-rich environment of a detonating bomb.