[en] Bound states of D-branes, for example the D2-D0 bound state, can be realized as solitons in the infinitely many D0-branes and anti-D0-branes with the nontrivial tachyon condensation. Both the commutative and noncommutative descriptions of the bound state are obtained by taking two different gauge choices of the D0-D0-bar-branes for the D2-D0 bound state. We can generalize this to other bound states of D-branes and show other equivalence relations between two seemingly different D-brane systems, including the D-brane realization of the ADHM construction of instanton. (author)