What does a pion do?
The pion can be thought of as one of the particles that mediate the residual strong interaction between a pair of nucleons. This interaction is attractive: it pulls the nucleons together. Written in a non-relativistic form, it is called the Yukawa potential.
What is pion made of?
The pion is a meson. The π+ is considered to be made up of an up and an anti-down quark. The neutral pion is considered to be a combination of quark-antiquark pairs: Pions interact with nuclei and transform a neutron to a proton or vice versa as indicated by the Feynman diagram above.
Are pions strange?
The pion, proton, and neutron have S = 0. Because the strong force conserves strangeness, it can produce strange particles only in pairs, in which the net value of strangeness is zero.