If you took Organic Chemistry, you will recall that stereochemistry occurs when the the compound has a chiral carbon (or other) atom. Look for chiral centers in your compound.

If your molecule has one or more chiral C, which that bonded with four different group/element, it shows stereoisomer. if the number of chiral C atom is n, There are 2n stereoisomers for that molecule. For example glyceraldehyde has one chiral C, so there are (21) 2 stereoisomer. But, dihydroxyaceton don't have stereoisomer due to lacking chiral C atom.

Stereochemistry is part & parcel of organic chemistry as well as other chemistry branches. This chemistry is concerned with the structure of molecules "small or large" in the space of 3-dimensions.

When you look at a good book of organic chemistry, you will see stereochemistry discussed for alkanes (e,g, staggered & eclipsed conformations), for alkenes (e,g. cis & trans configurations), for cycloalkanes (e.g. chair & boat conformations) and for other types of compounds which exist as (R) & (S) stereoisomers due to having a chiral center.The very existence of these isomers will cause a difference "e.g. R-lactic acid & S-lactic acid are different compounds". Add to it that there are R- & S-isomers with one of them being a medicine while the other is a poison. Fascinating field, indeed.

Of course, there are compounds which are not stereoisomers such as n-hexane & 2-methylpentane "skeletal isomers" and o-xylene & p-xylene "positional isomers".

Thanks everyone for your clarification