What do all acids and bases have in common?

Acid:

• Acids are substances that donate protons $\left({\mathrm{H}}^{+}\right)$.
• The pH of acidic solutions is below $7$.

Base:

• Bases are substances that accept protons $\left({\mathrm{H}}^{+}\right)$ when dissolved in water.
• The pH of basic solutions is above $7$.

Similarity between acid and base:

• Both acid and base conduct electricity as they produce $\left({\mathrm{H}}^{+}\right)$ and $\left({\mathrm{OH}}^{-}\right)$ ions respectively.
• Thus, both acid and base acts as an electrolyte.