What exactly are lewis acids and lewis bases?

Lewis acid are substance that contain H⁺ ion

for example;  

H₂o ⇒ H⁺ +  O₂

Lewis base are substance that contains OH⁻ ion

for example

NaOH ⇒ Na⁺  +  OH⁻

Lewis acid is  any substance, such as the H+ ion, that can accept a pair of nonbonding electrons. In other words, a Lewis acid is an electron-pair acceptor. e.g NH4+ and H3O.

A Lewis base is any substance, such as the OH- ion, that can donate a pair of nonbonding electrons. A Lewis base is therefore an electron-pair donor. e.g Water (H2O)