Explaining Ba(OH)2 as a base?
Barium hydroxide – or more exactly, the hydroxide ion – is a Brønsted-Lowry base, because in aqueous solution, it is completely dissociated into $\ce{Ba^2+}$ and $\ce{OH-}$ ions:

$$\ce{Ba(OH)2 -&gt; Ba^2+ + 2OH-}$$

$\ce{OH-}$ is a proton acceptor, forming $\ce{H2O}$. In aqueous solution, the following reaction takes place:

$$\ce{OH- + H3O+ -&gt;~ 2H2O}$$

Barium hydroxide thus reacts with acids in a neutralization reaction, with water and the barium salt of the respective acid as the products. For example, with hydrochloric acid:

$$\ce{Ba(OH)2 + 2HCl -&gt;~ BaCl2 + 2H2O}$$