At sufficiently low temperatures, electrons near the Fermi surface become unstable against the formation of Cooper pairs. Cooper showed such binding will occur in the presence of an attractive potential, no matter how weak. In conventional superconductors, an attraction is generally attributed to an electron-lattice interaction. The BCS theory, however, requires only that the potential be attractive, regardless of its origin. In the BCS framework, superconductivity is a macroscopic effect which results from the condensation of Cooper pairs. These have some bosonic properties, and bosons, at sufficiently low temperature, can form a large Bose–Einstein condensate. Superconductivity was simultaneously explained by Nikolay Bogolyubov, by means of the Bogoliubov transformations.
Summarize the mechanism for conventional superconductors.
Cooper Pairs - consisting of two lightly attracted electrons - still carry charge, but now act more like bosons than fermions.  Unlike fermions, bosons can all behave the exact same. Cooper Pairs all "acting the same" is the mechanism of conventional superconductivity.