Here's why:

* Acids donate H+ ions (protons) to a solution, increasing the concentration of H+ ions.

* Bases accept H+ ions from a solution, decreasing the concentration of H+ ions.

There are different ways bases can remove H+ from a solution:

* Hydroxide ions (OH-) directly react with H+ ions to form water:

* H+ + OH- -> H2O

* Other bases may react with H+ to form a new compound, effectively removing the H+ from solution.

Examples of bases:

* Sodium hydroxide (NaOH) - a strong base that readily dissociates in water to form OH- ions.

* Ammonia (NH3) - a weak base that reacts with water to form ammonium (NH4+) ions and OH- ions.

* Calcium carbonate (CaCO3) - a solid base that reacts with acids to neutralize them.

Note: The strength of a base refers to its ability to accept H+ ions. Strong bases completely dissociate in water, while weak bases only partially dissociate.