StrongA strong acid (baseor base) forms a weak conjugate base (acidor acid). This is correct. By saying that HA$\ce{HA}$ is a weak acid and A-$\ce{A-}$ is a weak conjugate base they mean:
Acid shouldn't be too strong - don't use NaCl+HCl
Conjugated base shouldn't be too strong - don't use EtOH/NaOEt
Use a "not-strong" acid (weak acid) who's conjugate base is also "not-strong" (weak conjugate base)
H3CCOOH is a relatively weak acid. But H3CCOONa is also a relatively weak base. Choose such acids to make a buffer.
- Acid shouldn't be too strong - don't use $\ce{NaCl + HCl }$
- Conjugated base shouldn't be too strong - don't use $\ce{EtOH/NaOEt }$
- Use a "not-strong" acid (weak acid) whose conjugate base is also "not-strong" (weak conjugate base). For example, $\ce{H3CCOOH}$ is a relatively weak acid. But $\ce{H3CCOONa}$ is also a relatively weak base. Choose such acids to make a buffer.
