What is Indistinguishable particles, antisymmetric wavefunction?

Particles are indistinguishable if no measurement can tell them apart: every electron is identical to every other. A wavefunction of several electrons is an antisymmetric wavefunction if it changes sign when the coordinates (space and spin) of any two electrons are exchanged: $\Psi(\dots,i,\dots,j,\dots) = -\Psi(\dots,j,\dots,i,\dots)$.