NaOH is a strong base, so it separates. Acetic acid is really weak so it remains as whole. NaCH3COO(aq) separates because it is a salt.
CH3COOH(aq) + Na^+ + OH^- ---> Na^+ + CH3COO^- + H2O
Na cancels
net ionic equation:
CH3COOH(aq) + OH^- ---> CH3COO^- + H2O
CH3COOH(aq) + Na^+ + OH^- ---> Na^+ + CH3COO^- + H2O
Na cancels
net ionic equation:
CH3COOH(aq) + OH^- ---> CH3COO^- + H2O