when is it used h+ and oh- in chemical reaction?

ANSWER :-

Use of H+ in chemical reaction -----> Substances which liberates H+ ion in chemical reaction are categorised as acids. H+ ion generally in a chemical reaction means hydronium or hydrogen ions which also decides the basicity of a compound.

Use of OH- in chemical reaction-----> Substances which liberates OH-ion in a chemical reaction are categorised as bases.OH- ion generally in a chemical reaction means hydroxide  ions which also decides the acidity of  a compound.

Example of a chemical reaction involving H+ ions :- Hcl ----on heating-----> (H+) + (cl-)

Example of a chemical reaction involving OH- ion :- NaOH ------on heating-----> (Na+) + (OH-)

(Here Hcl is an acid and NaOH is a base.)