beer / bier are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
beer: (noun) a general name for alcoholic beverages made by fermenting a cereal (or mixture of cereals) flavored with hops.
bier: (noun) a coffin along with its stand. (noun) a stand to support a corpse or a coffin prior to burial.
beer: b·IH·r
bier: b·IY·r
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)