I will talk about hyperons. Hyperons are not fundamental particles because they are made up by quarks, like neutrons or protons.
(to see what are quarks check this post: https://dragallur.wordpress.com/2015/05/03/3-particles-quarks/)
They are in the group of hadrons. It is group of particles that are made up by quarks so in this group are also Pions which are in the smaller group of mesons.
Btw. mesons are particles that are made up by pair of quark-antiquark.
While hyperons are in the group of baryons = particles with three quarks.
So the strange thing about them is that they have to have one strange quark so they can be hyperons. The most “common” one is similar to proton or neutron because he is made up of up, down and strange quark and he is called Lambda. There are twelve of them with different combinations of those three quarks, one of them, Omega has only strange quarks.
Ok, thats about it. They have also attribute of really fast decaying because strange quark is not very stable so they can not be found except in Hyperon stars. Those are heavier neutron stars in which hyperons wont decay because they have no space and gravity will hold them.